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

11, 18, 21, 25, 32, 39, 43, 46, 49, 54, 60, 65, 67, 68, 74, 76, 81, 87, 88, 90, 95, 98, 106, 109, 111, 113, 116, 120, 123, 125, 130, 136, 137, 142, 144, 153, 158, 159, 163, 164, 165, 172, 173, 175, 179, 182, 186, 193, 197, 201, 204, 205, 207, 208, 214, 219, 220

Offset

1,1

Links

Robert Israel, Table of n, a(n) for n = 1..10000

Maple

GP:= [0, seq(op([m*(3*m-1)/2, m*(3*m+1)/2]), m=1..50)]:
N:= GP[-1]:
V:= Array(0..N, datatype=integer[4]):
for i from 1 to nops(GP) do
for j from 1 to i do
   r:= GP[i]+GP[j];
   if r > N then break fi;
   V[r]:= V[r]+1
od od:
select(t -> V[t] = 0, [$0..N]); # Robert Israel, Feb 26 2025

Crossrefs

Cf. A001318 (generalized pentagonal numbers), A093518.

Cf. A204382.

Sequence in context: A300062 A309489 A054306 * A031119 A242918 A287868

Adjacent sequences: A093516 A093517 A093518 * A093520 A093521 A093522

Keyword

nonn,changed

Author

Jon Perry, Mar 29 2004

Extensions

Definition clarified by Robert Israel, Feb 26 2025

Status

approved