cp's OEIS Frontend

A093519 Numbers with no representation as the sum of two (not necessarily distinct) generalized pentagonal numbers.

%I A093519 #12 Feb 27 2025 08:26:06
%S A093519 11,18,21,25,32,39,43,46,49,54,60,65,67,68,74,76,81,87,88,90,95,98,
%T A093519 106,109,111,113,116,120,123,125,130,136,137,142,144,153,158,159,163,
%U A093519 164,165,172,173,175,179,182,186,193,197,201,204,205,207,208,214,219,220
%N A093519 Numbers with no representation as the sum of two (not necessarily distinct) generalized pentagonal numbers.
%H A093519 Robert Israel, <a href="/A093519/b093519.txt">Table of n, a(n) for n = 1..10000</a>
%p A093519 GP:= [0, seq(op([m*(3*m-1)/2, m*(3*m+1)/2]), m=1..50)]:
%p A093519 N:= GP[-1]:
%p A093519 V:= Array(0..N, datatype=integer[4]):
%p A093519 for i from 1 to nops(GP) do
%p A093519 for j from 1 to i do
%p A093519    r:= GP[i]+GP[j];
%p A093519    if r > N then break fi;
%p A093519    V[r]:= V[r]+1
%p A093519 od od:
%p A093519 select(t -> V[t] = 0, [$0..N]); # _Robert Israel_, Feb 26 2025
%Y A093519 Cf. A001318 (generalized pentagonal numbers), A093518.
%Y A093519 Cf. A204382.
%K A093519 nonn
%O A093519 1,1
%A A093519 _Jon Perry_, Mar 29 2004
%E A093519 Definition clarified by _Robert Israel_, Feb 26 2025