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%I #27 Feb 01 2021 11:49:05
%S 20,47,104,113,228,255,333,544,632,743,1054,1122,1518,1762,1901,2071,
%T 3617,4317,4432,4456,4513,4557,4727,4927,5000,5058,5080,5173,5473,
%U 5847,6047,6767,6832,7247,7408,7453,7487,7518,7921,7997,8127,8958,9208,9487,10917
%N Numbers k such that k + the sum of the 4th powers of the decimal digits of k is a square.
%e 20 is a member since 2^4 + 0^4 + 20 = 6^2,
%e 47 is a member since 4^4 + 7^4 + 47 = 52^2,
%e 104 is a member since 1^4 + 0^4 + 4^4 = 104 = 19^2,
%e 113 is a member since 1^4 + 1^4 + 3^4 + 113 = 14^2.
%p filter:= proc(n) local L,k;
%p issqr(n + add(t^4, t=convert(n,base,10)))
%p end proc:
%p select(filter, [$1..20000]); # _Robert Israel_, Jan 30 2021
%Y Cf. A055013, A329179, A329386.
%K base,nonn
%O 1,1
%A _Will Gosnell_, Jan 30 2021
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