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

0,2

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

Links

Table of n, a(n) for n=0..18.

Crossrefs

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

See also A029744, A354169.

Sequence in context: A192415 A201779 A067149 * A344782 A191240 A208952

Adjacent sequences: A354147 A354148 A354149 * A354151 A354152 A354153

Keyword

nonn,more

Author

N. J. A. Sloane, May 26 2022

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

Status

approved