Duffinian numbers: Difference between revisions

=={{header|Nim}}==

{{trans|ALGOL 68}}

<syntaxhighlight lang="Nim">import std/[algorithm, math, strformat]

const MaxNumber = 500_000

# Construct a table of the divisor counts.

var ds: array[1..MaxNumber, int]

ds.fill 1

for i in 2..MaxNumber:

for j in countup(i, MaxNumber, i):

ds[j] += i

# Set the divisor counts of non-Duffinian numbers to 0.

ds[1] = 0 # 1 is not Duffinian.

for n in 2..MaxNumber:

let nds = ds[n]

if nds == n + 1 or gcd(n, nds) != 1:

# "n" is prime or is not relatively prime to its divisor sum.

ds[n] = 0

# Show the first 50 Duffinian numbers.

echo "First 50 Duffinian numbers:"

var dcount = 0

var n = 1

while dcount < 50:

if ds[n] != 0:

stdout.write &" {n:3}"

inc dcount

if dcount mod 25 == 0:

echo()

inc n

echo()

# Show the Duffinian triplets below MaxNumber.

echo &"The Duffinian triplets up to {MaxNumber}:"

dcount = 0

for n in 3..MaxNumber:

if ds[n - 2] != 0 and ds[n - 1] != 0 and ds[n] != 0:

inc dcount

stdout.write &" {(n - 2, n - 1, n): ^24}"

stdout.write if dcount mod 4 == 0: '\n' else: ' '

echo()

</syntaxhighlight>

{{out}}

The output is identical to that of the Algol 68 program, but the formatting is different.

<pre>First 50 Duffinian numbers:

4 8 9 16 21 25 27 32 35 36 39 49 50 55 57 63 64 65 75 77 81 85 93 98 100

111 115 119 121 125 128 129 133 143 144 155 161 169 171 175 183 185 187 189 201 203 205 209 215 217

The Duffinian triplets up to 500000:

(63, 64, 65) (323, 324, 325) (511, 512, 513) (721, 722, 723)

(899, 900, 901) (1443, 1444, 1445) (2303, 2304, 2305) (2449, 2450, 2451)

(3599, 3600, 3601) (3871, 3872, 3873) (5183, 5184, 5185) (5617, 5618, 5619)

(6049, 6050, 6051) (6399, 6400, 6401) (8449, 8450, 8451) (10081, 10082, 10083)

(10403, 10404, 10405) (11663, 11664, 11665) (12481, 12482, 12483) (13447, 13448, 13449)

(13777, 13778, 13779) (15841, 15842, 15843) (17423, 17424, 17425) (19043, 19044, 19045)

(26911, 26912, 26913) (30275, 30276, 30277) (36863, 36864, 36865) (42631, 42632, 42633)

(46655, 46656, 46657) (47523, 47524, 47525) (53137, 53138, 53139) (58563, 58564, 58565)

(72961, 72962, 72963) (76175, 76176, 76177) (79523, 79524, 79525) (84099, 84100, 84101)

(86527, 86528, 86529) (94177, 94178, 94179) (108899, 108900, 108901) (121103, 121104, 121105)

(125315, 125316, 125317) (128017, 128018, 128019) (129599, 129600, 129601) (137287, 137288, 137289)

(144399, 144400, 144401) (144721, 144722, 144723) (154567, 154568, 154569) (158403, 158404, 158405)

(166463, 166464, 166465) (167041, 167042, 167043) (175231, 175232, 175233) (177607, 177608, 177609)

(181475, 181476, 181477) (186623, 186624, 186625) (188497, 188498, 188499) (197191, 197192, 197193)

(199711, 199712, 199713) (202499, 202500, 202501) (211249, 211250, 211251) (230399, 230400, 230401)

(231199, 231200, 231201) (232561, 232562, 232563) (236195, 236196, 236197) (242063, 242064, 242065)

(243601, 243602, 243603) (248003, 248004, 248005) (260099, 260100, 260101) (260641, 260642, 260643)

(272483, 272484, 272485) (274575, 274576, 274577) (285155, 285156, 285157) (291599, 291600, 291601)

(293763, 293764, 293765) (300303, 300304, 300305) (301087, 301088, 301089) (318095, 318096, 318097)

(344449, 344450, 344451) (354481, 354482, 354483) (359551, 359552, 359553) (359999, 360000, 360001)

(367235, 367236, 367237) (374543, 374544, 374545) (403201, 403202, 403203) (406801, 406802, 406803)

(417697, 417698, 417699) (419903, 419904, 419905) (423199, 423200, 423201) (435599, 435600, 435601)

(468511, 468512, 468513) (470449, 470450, 470451) (488071, 488072, 488073)

</pre>