A354150 Index of 2^n in A090252, or -1 if 2^n does not appear.

1, 2, 5, 11, 23, 95, 191, 383, 1535, 6143, 24575, 49151, 196607, 786431, 3145727, 12582911, 50331647, 201326591, 805306367

Offset: 0

Author

N. J. A. Sloane, May 26 2022

Keywords

• nonn
• more

Comments

It is conjectured (see A090252) that the indices of even terms in A090252 are {3*2^i-1, i >= 0} (A083329), so the positive terms of the present sequence should be a subsequence of A083329.

For n = 1,...,18, the terms are 3*2^k - 1 for k = 0,1,2,3,5,6,7,9,11,13,14,16,18,20,22,24,26,28. Will the formula a(n) = 3*2^(2*n-8)-1 hold for all n >= 11? This appears to be yet another example of the influence of A029744 on A090252 and A354691.- N. J. A. Sloane, Aug 24 2022

Crossrefs

Cf. A090252, A083329, A354148, A354149, A354255 (even terms in A090252).

See also A029744, A354169.

Extensions

a(10) from Michael S. Branicky, May 27 2022

a(11)-a(14) from Michael S. Branicky, Jun 01 2022 using gzipped b-file at A090252

a(15)-a(18) from Jinyuan Wang, Jul 15 2022