A133923 - OEIS

A133923

a(1)=1, and for n>1, a(n) = a(n-1)/2, if a(n-1) is divisible by 2, otherwise a(n) = A000005(n*a(n-1)).

1, 2, 1, 3, 4, 2, 1, 4, 2, 1, 2, 1, 2, 1, 4, 2, 1, 6, 3, 12, 6, 3, 4, 2, 1, 4, 2, 1, 2, 1, 2, 1, 4, 2, 1, 9, 6, 3, 6, 3, 4, 2, 1, 6, 3, 8, 4, 2, 1, 6, 3, 12, 6, 3, 8, 4, 2, 1, 2, 1, 2, 1, 6, 3, 8, 4, 2, 1, 4, 2, 1, 12, 6, 3, 9, 18, 9, 16, 8, 4, 2, 1, 2, 1, 4, 2, 1, 8, 4, 2, 1, 6, 3, 8, 4, 2, 1, 6, 3, 18

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OFFSET

1,2

COMMENTS

The formula could be generalized to a class of sequences as a(n)= A000005(A*a(n-1)+B) if a(n-1) is not divisible by C, else a(n)= a(n-1)/C, where A, B, C are integers. In this case we have A=n, B=0 and C=2.

LINKS

Table of n, a(n) for n=1..100.

PROG

(MIT/GNU Scheme) (define (A133923 n) (cond ((< n 2) n) ((even? (A133923 (-1+ n))) (/ (A133923 (-1+ n)) 2)) (else (A000005 (* n (A133923 (-1+ n)))))))

CROSSREFS

Cf. A000005.

Sequence in context: A286539 A004741 A352840 * A347296 A341231 A334081

Adjacent sequences: A133920 A133921 A133922 * A133924 A133925 A133926

KEYWORD

nonn

AUTHOR

Ctibor O. Zizka, Jan 07 2008

EXTENSIONS

Edited, corrected, extended and Scheme-code added by Antti Karttunen, Oct 05 2009

STATUS

approved