A253790 - OEIS

A253790

a(1) = 1; thereafter, odd numbers such that A055396(n) = A001511(n-1).

1, 3, 5, 15, 27, 39, 51, 63, 75, 85, 87, 99, 111, 123, 125, 135, 147, 159, 171, 183, 195, 205, 207, 209, 217, 219, 231, 243, 245, 255, 267, 279, 291, 303, 315, 325, 327, 329, 339, 351, 363, 365, 375, 387, 399, 411, 423, 435, 445, 447, 459, 471, 481, 483, 485, 495, 507, 519, 531, 543, 553, 555

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,2

COMMENTS

After 1, all such odd numbers whose smallest prime factor A020639(n) = A000040(k+1), where k = A007814(n-1), the 2-adic valuation of the preceding even number.

Any odd number present in A253789 must be one of these terms.

LINKS

Antti Karttunen, Table of n, a(n) for n = 1..10000

PROG

(Scheme) ;; With Antti Karttunen's IntSeq-library.

(define A253790 (MATCHING-POS 1 1 (lambda (n) (or (= 1 n) (and (odd? n) (= (A055396 n) (A001511 (- n 1))))))))

CROSSREFS

Cf. A000040, A001511, A007814, A020639, A029747, A055396, A253789.

Sequence in context: A321985 A301524 A202212 * A372430 A053351 A289045

Adjacent sequences: A253787 A253788 A253789 * A253791 A253792 A253793

KEYWORD

nonn

AUTHOR

Antti Karttunen, Jan 13 2015

STATUS

approved