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A340494 Index where n first appears in A340488. 5
1, 3, 6, 8, 16, 18, 21, 23, 56, 58, 61, 63, 71, 73, 76, 78, 216, 218, 221, 223, 231, 233, 236, 238, 271, 273, 276, 278, 286, 288, 291, 293, 856, 858, 861, 863, 871, 873, 876, 878, 911, 913, 916, 918, 926, 928, 931, 933, 1071, 1073, 1076, 1078, 1086, 1088, 1091 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

The first differences appear to be some kind of ruler sequence separated by 2's.

indeed, the first differences look like n -> f(A001511(n)) with f = (2, 3, 8, 33, 138, 563, 2268, 9093, 36398, 145623, 582528, 2330153, 9320658, etc.). See A340495. - Rémy Sigrist, Jan 10 2021

LINKS

Rémy Sigrist, Table of n, a(n) for n = 0..8191

Rémy Sigrist, PARI program for A340494

FORMULA

The generating function appears to be

1/(1-x ) + 2*x/(1-x)^2 + (1/(1-x))*Sum_{t>=1} x^(2^t)*(g(t+1)-g(t))/(1-x^(2^t)),

where g = {g(t): t >= 1} = 2,3,8,33,138,... has g.f. x*(2*x-1)*(2*x^2+5*x-2)/((1-x)^2*(1-4*x)). - Rémy Sigrist and N. J. A. Sloane, Jan 10 2021

PROG

(PARI) See Links section.

CROSSREFS

Cf. A001511, A340488, A340495.

Sequence in context: A117148 A305595 A320687 * A039567 A032912 A123208

Adjacent sequences:  A340491 A340492 A340493 * A340495 A340496 A340497

KEYWORD

nonn

AUTHOR

N. J. A. Sloane, Jan 10 2021

EXTENSIONS

More terms from Rémy Sigrist, Jan 10 2021

STATUS

approved

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Last modified May 18 19:02 EDT 2021. Contains 344001 sequences. (Running on oeis4.)