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A267696 Numbers with 5 odd divisors. 7
81, 162, 324, 625, 648, 1250, 1296, 2401, 2500, 2592, 4802, 5000, 5184, 9604, 10000, 10368, 14641, 19208, 20000, 20736, 28561, 29282, 38416, 40000, 41472, 57122, 58564, 76832, 80000, 82944, 83521, 114244, 117128, 130321, 153664, 160000, 165888, 167042, 228488, 234256, 260642, 279841 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Positive integers that have exactly five odd divisors.

Numbers n such that the symmetric representation of sigma(n) has 5 subparts. - Omar E. Pol, Dec 28 2016

Also numbers that can be expressed as the sum of k > 1 consecutive positive integers in exactly 4 ways; e.g., 81 = 40+41 = 26+27+28 = 11+12+13+14+15+16 = 5+6+7+8+9+10+11+12+13. - Julie Jones, Aug 13 2018

LINKS

Table of n, a(n) for n=1..42.

FORMULA

A001227(a(n)) = 5.

PROG

(PARI) isok(n) = sumdiv(n, d, (d%2)) == 5; \\ Michel Marcus, Apr 03 2016

(GAP) A:=List([1..700000], n->DivisorsInt(n));;

B:=List([1..Length(A)], i->Filtered(A[i], IsOddInt));;

a:=Filtered([1..Length(B)], i->Length(B[i])=5); # Muniru A Asiru, Aug 14 2018

CROSSREFS

Column 5 of A266531.

Cf. A001227, A030514, A038547, A236104, A237593, A279387.

Numbers with k odd divisors (k = 1..10): A000079, A038550, A072502, apparently A131651, this sequence, A230577, A267697, A267891, A267892, A267893.

Sequence in context: A044632 A031494 A043324 * A232923 A250655 A184003

Adjacent sequences:  A267693 A267694 A267695 * A267697 A267698 A267699

KEYWORD

nonn

AUTHOR

Omar E. Pol, Apr 03 2016

EXTENSIONS

More terms from Michel Marcus, Apr 03 2016

STATUS

approved

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Last modified December 11 10:48 EST 2018. Contains 318049 sequences. (Running on oeis4.)