Original entry on oeis.org
3, 11, 197, 103049
Offset: 1
-
s(m)= { if (m==1, return(a1)); if (m==2, return(a2)); r = (3*(2*m - 3)*a2 - (m - 3)*a1)/m; a1=a2; a2=r; return(r); }
{ a1=1; a2=1; n=0; for (m=1, 300, a=s(m); if (isprime(a), n++; print1(a, ", "))); } \\ Harry J. Smith, Jun 21 2009
A092838
Numerators in the series for sec(x) that are primes.
Original entry on oeis.org
5, 61, 277, 23489580527043108252017828576198947741, 5516994249383296071214195242422482492286460673697
Offset: 1
Original entry on oeis.org
7, 11, 17, 19, 21, 239
Offset: 1
a(1) = 7 because A001003(7) = 4279 = 11 * 389.
a(2) = 11 because A001003(11) = 2646723 = 3 * 882241.
a(3) = 17 because A001003(17) = 55909013009 = 41263 * 1354943.
a(4) = 19 because A001003(19) = 1618362158587 = 24413 * 66290999.
a(5) = 21 because A001003(21) = 47574827600981 = 3253 * 14624908577.
- Eric Weisstein's World of Mathematics, Semiprime.
Original entry on oeis.org
4279, 2646723, 55909013009, 1618362158587, 47574827600981
Offset: 1
- Eric Weisstein's World of Mathematics, Semiprime.
Showing 1-4 of 4 results.
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