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A267697 Numbers with 7 odd divisors. 8
729, 1458, 2916, 5832, 11664, 15625, 23328, 31250, 46656, 62500, 93312, 117649, 125000, 186624, 235298, 250000, 373248, 470596, 500000, 746496, 941192, 1000000, 1492992, 1771561, 1882384, 2000000, 2985984, 3543122, 3764768, 4000000, 4826809, 5971968, 7086244, 7529536, 8000000, 9653618 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Positive integers that have exactly seven odd divisors.

Numbers n such that the symmetric representation of sigma(n) has 7 subparts. - Omar E. Pol, Dec 28 2016

Numbers that can be formed in exactly 6 ways by summing sequences of 2 or more consecutive positive integers. - Julie Jones, Aug 13 2018

Numbers of the form p^6 * 2^k where p is an odd prime. - David A. Corneth, Aug 14 2018

LINKS

David A. Corneth, Table of n, a(n) for n = 1..10000

FORMULA

A001227(a(n)) = 7.

PROG

(PARI) isok(n) = sumdiv(n, d, (d%2)) == 7; \\ Michel Marcus, Apr 03 2016

(PARI) upto(n) = {my(res = List()); forprime(p = 3, sqrtnint(n, 6), listput(res, p^6)); q = #res; for(i = 1, q, odd = res[i]; for(j = 1, logint(n \ odd, 2), listput(res, odd <<= 1))); listsort(res); res} \\ David A. Corneth, Aug 14 2018

CROSSREFS

Column 7 of A266531.

Cf. A001227, A030516, A038547, A236104, A237593, A279387.

Numbers with k odd divisors (k = 1..10): A000079, A038550, A072502, apparently A131651, A267696, A230577, this sequence, A267891, A267892, A267893.

Sequence in context: A046319 A119710 A043455 * A232925 A255112 A255627

Adjacent sequences:  A267694 A267695 A267696 * A267698 A267699 A267700

KEYWORD

nonn,easy

AUTHOR

Omar E. Pol, Apr 03 2016

EXTENSIONS

More terms from Michel Marcus, Apr 03 2016

STATUS

approved

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Last modified September 25 19:24 EDT 2018. Contains 315394 sequences. (Running on oeis4.)