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A225091 The odd part of the digit sum of 7^n. 2
1, 7, 13, 5, 7, 11, 7, 25, 31, 7, 43, 49, 37, 13, 29, 1, 13, 29, 73, 79, 19, 41, 97, 85, 73, 97, 7, 91, 133, 121, 59, 115, 103, 127, 71, 157, 17, 115, 65, 17, 71, 37, 17, 169, 175, 163, 187, 175, 17, 89, 23, 217, 49, 55, 217, 107, 211, 181, 241, 211, 199, 205 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

Conjecture: the sequence contains all primes > 3.

LINKS

Peter J. C. Moses, Table of n, a(n) for n = 0..1999

FORMULA

a(n) = A000265(A066003(n)). - R. J. Mathar, May 05 2013

MAPLE

read(transforms) :

A225091 := proc(n)

    A000265(digsum(7^n)) ;

end proc: # R. J. Mathar, May 05 2013

MATHEMATICA

Map[#/(2^IntegerExponent[#, 2])&[Total[IntegerDigits[7^#]]]&, Range[0, 99]] (* Peter J. C. Moses, Apr 27 2013 *)

PROG

(PARI) a(n) = my(s = sumdigits(7^n)); s >> valuation(s, 2); \\ Michel Marcus, Dec 19 2018

CROSSREFS

Cf. A221858, A225017, A225039, A225040.

Sequence in context: A299472 A285642 A209189 * A225516 A125741 A103705

Adjacent sequences:  A225088 A225089 A225090 * A225092 A225093 A225094

KEYWORD

nonn,base

AUTHOR

Vladimir Shevelev, Apr 27 2013

STATUS

approved

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Last modified July 22 20:51 EDT 2019. Contains 325226 sequences. (Running on oeis4.)