A342469 Positive numbers that are triangular, square or pentagonal.

1, 3, 4, 5, 6, 9, 10, 12, 15, 16, 21, 22, 25, 28, 35, 36, 45, 49, 51, 55, 64, 66, 70, 78, 81, 91, 92, 100, 105, 117, 120, 121, 136, 144, 145, 153, 169, 171, 176, 190, 196, 210, 225, 231, 247, 253, 256, 276, 287, 289, 300, 324, 325, 330, 351, 361, 376, 378, 400

Offset

1,2

Links

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

Maple

N:= 1000: # for terms <= N
sort(convert({seq(i^2, i=1..floor(sqrt(N))), seq(i*(i+1)/2, i=1 .. (floor(sqrt(1+8*N))-1)/2),
seq(i*(3*i-1)/2, i=1..(floor(sqrt(1+24*N))+1)/6)}, list)); # Robert Israel, Nov 11 2025

Prog

(PARI) isok(m) = ispolygonal(m, 3) || ispolygonal(m, 4) || ispolygonal(m, 5);

Crossrefs

Cf. A000290, A000217, A000326, A005214.

Cf. A245646, A245647, A245648.

Sequence in context: A081944 A129948 A050414 * A266322 A136681 A206330

Adjacent sequences: A342466 A342467 A342468 * A342470 A342471 A342472

Keyword

nonn

Author

Michel Marcus, Mar 13 2021

Status

approved