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 A257591 Odd numbers which are not prime powers but which have a proper divisor == 1 mod 4. 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

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Last modified December 1 23:26 EST 2023. Contains 367503 sequences. (Running on oeis4.)