A036924 Digit sum of composite even number equals digit sum of juxtaposition of its prime factors (counted with multiplicity).
4, 22, 58, 94, 166, 202, 274, 346, 378, 382, 438, 454, 526, 562, 576, 588, 634, 636, 648, 654, 666, 690, 706, 728, 762, 778, 852, 922, 958, 1086, 1282, 1284, 1376, 1626, 1642, 1678, 1736, 1776, 1822, 1842, 1858, 1872, 1894, 1908, 1952, 1962, 1966, 2038
Offset: 1
Links
- Robert Israel, Table of n, a(n) for n = 1..10000
Programs
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Maple
filter:= proc(n) local F; F:= ifactors(n)[2]; convert(convert(n,base,10),`+`) = convert(map(t -> t[2]*convert(convert(t[1],base,10),`+`), F),`+`) end proc: select(filter, [seq(i,i=4..10000,2)]); # Robert Israel, Aug 24 2024
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Mathematica
d[n_] := IntegerDigits[n]; co[n_,k_] := Nest[Flatten[d[{#,n}]]&, n, k-1]; t={}; Do[If[!PrimeQ[n] && Total[d[n]] == Total[Flatten[d[co@@@FactorInteger[n]]]], AppendTo[t,n]], {n,4,2040,2}]; t (* Jayanta Basu, Jun 04 2013 *)
Extensions
Title made more precise by Sean A. Irvine, Nov 30 2020
Comments