A076550 Indices of triangular numbers listed in A075088.

1, 2, 3, 7, 8, 15, 32, 64, 63, 224, 255, 1280, 512, 3968, 6399, 10240, 4095, 14336, 32768, 65535, 229375, 180224, 483327, 262143, 2097151, 1048575, 14680064, 17432576, 33554432, 67108864, 16777215

Offset: 0

Author

Shyam Sunder Gupta, Oct 19 2002

Keywords

• nonn

Comments

a(32) = 134217728. - Robert G. Wilson v, Jun 28 2010

Links

• Donovan Johnson, Table of n, a(n) for n = 0..51

Crossrefs

Cf. A000217, A075088.

Programs

Mathematica

f[n_] := Plus @@ Last /@ FactorInteger@n; t = Table[0, {100}]; k = 1; While[k < 10^9/4, a = f[k] + f[k + 1] -1; If[ t[[a + 1]] == 0, t[[a + 1]] = k; Print[{a, k}]]; k++ ]; t (* Robert G. Wilson v, Jun 28 2010 *)

Formula

A000217(a(n)) = A075088(n).

Extensions

Edited by Ray Chandler, Dec 17 2004

a(26)-a(30) from Ray Chandler, Dec 22 2004