A100874 Number of terms of A100873 less than 10^n.

0, 0, 1, 6, 29, 68, 156, 381, 974, 2406, 5717, 13521, 32431, 78238, 189831, 464411, 1150499, 2881028, 7289744

Offset

1,4

Links

Table of n, a(n) for n=1..19.

Prog

(PARI) twtotwp2(n, n2, k) = { local(x, y, x2, c); c=0; forprime(x=n, n2, x2=x+2; y=x^x2+k; if(y%x2==0 && !isprime(x2), c++; print1(x+2", "); ); ); print(); print(c", "pitwin(n2)) }
pitwins(n) = \\The number of twin prime pairs <= n.
{ local(c, x); c=0; forprime(x=3, n, if(isprime(x+2), c++) ); return(c) }

Crossrefs

Cf. A100873.

Sequence in context: A178366 A175956 A164274 * A047923 A006816 A184130

Adjacent sequences: A100871 A100872 A100873 * A100875 A100876 A100877

Keyword

nonn,hard,more

Author

Cino Hilliard, Jan 09 2005

Extensions

Offset corrected and a(6)-a(19) added by Amiram Eldar, Jan 10 2020

Status

approved