A257591 - OEIS

A257591

Odd numbers which are not prime powers but which have a proper divisor == 1 mod 4.

15, 35, 39, 45, 51, 55, 63, 65, 75, 85, 87, 91, 95, 99, 105, 111, 115, 117, 119, 123, 135, 143, 145, 147, 153, 155, 159, 165, 171, 175, 183, 185, 187, 189, 195, 203, 205, 207, 215, 219, 221, 225, 231, 235, 245, 247, 255, 259, 261, 265, 267, 273, 275, 279, 285

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

OFFSET

1,1

LINKS

Hiroaki Yamanouchi, Table of n, a(n) for n = 1..3124

R. Lauterbach, Equivariant Bifurcation and Absolute Irreducibility in R^8: A Contribution to Ize Conjecture and Related Bifurcations, Journal of Dynamics and Differential Equations, Oct 2014; DOI 10.1007/s10884-014-9402-1.

EXAMPLE

63 = 7*9 is not a power of a prime and has a proper divisor 9 == 1 mod 4.

PROG

(PARI) lista(nn) = {forstep(n=1, nn, 2, if (!isprimepower(n) && sumdiv(n, d, (d != 1) && (d != n) && ((d % 4)==1)), print1(n, ", ")); ); } \\ Michel Marcus, Jun 19 2015

CROSSREFS

Subsequence of A061346.

Sequence in context: A338063 A111170 A134335 * A284406 A329589 A356794

Adjacent sequences: A257588 A257589 A257590 * A257592 A257593 A257594

KEYWORD

nonn

AUTHOR

N. J. A. Sloane, May 14 2015

EXTENSIONS

a(7)=57 removed and a(11)-a(55) added by Hiroaki Yamanouchi, May 20 2015

STATUS

approved