A004625 - OEIS

A004625

Numbers divisible only by primes congruent to 1 mod 8.

1, 17, 41, 73, 89, 97, 113, 137, 193, 233, 241, 257, 281, 289, 313, 337, 353, 401, 409, 433, 449, 457, 521, 569, 577, 593, 601, 617, 641, 673, 697, 761, 769, 809, 857, 881, 929, 937, 953, 977, 1009, 1033, 1049

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OFFSET

1,2

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 1..1000

MATHEMATICA

ok[n_] := And @@ (#1[[2]] == 1 && Mod[#1[[1]], 8] == 1 & ) /@ FactorInteger[n]; Select[ Range[2000], ok] (* Jean-François Alcover, Mar 09 2012 *)

PROG

(Magma) [n: n in [1..2000] | forall{d: d in PrimeDivisors(n) | d mod 8 eq 1}]; // Vincenzo Librandi, Aug 20 2012

(PARI) is(n)=is(n%8!=1, return(0)); my(f=factor(n)[, 1]); for(i=1, #f~, if(f[i]%8!=1, return(0))); 1 \\ Charles R Greathouse IV, Jul 02 2016

CROSSREFS

Sequence in context: A263011 A263012 A172280 * A141174 A007519 A163185

Adjacent sequences: A004622 A004623 A004624 * A004626 A004627 A004628

KEYWORD

nonn

AUTHOR

N. J. A. Sloane

EXTENSIONS

Offset changed from 0 to 1 by Vincenzo Librandi, Aug 20 2012

STATUS

approved