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

Offset: 1

Author

N. J. A. Sloane, May 14 2015

Keywords

• nonn

Examples

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

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.

Crossrefs

Subsequence of A061346.

Programs

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

Extensions

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