A163926 Number of nonprime numbers k such that the largest divisor of n*k <= sqrt(n*k) is n.

1, 1, 3, 3, 6, 4, 10, 6, 8, 7, 16, 6, 22, 12, 11, 9, 30, 9, 38, 11, 17, 18, 48, 11, 26, 24, 20, 14, 61, 13, 72, 18, 28, 32, 29, 13, 87, 40, 33, 18, 101, 17, 115, 25, 26, 50, 131, 19, 59, 29, 44, 29, 151, 23, 47, 24, 52, 63, 171, 20, 189, 75, 40, 32, 55, 27, 211, 42, 66, 31, 232

Offset

1,3

Links

Reinhard Zumkeller, Table of n, a(n) for n = 1..225

Prog

(PARI) a(n)=local(r, d); r=0; for(k=n, n^2, if(!isprime(k), d=divisors(n*k); if(n==d[(#d+1)\2], r++))); r
(Haskell)
a163926 = length . a163925_row  -- Reinhard Zumkeller, Mar 15 2014

Crossrefs

Row lengths of A163925.

Sequence in context: A265703 A070952 A137462 * A362334 A050346 A319619

Adjacent sequences: A163923 A163924 A163925 * A163927 A163928 A163929

Keyword

nonn

Author

Franklin T. Adams-Watters, Aug 06 2009

Status

approved