A071807 Number of pairs (x,y) such that prime(x) - prime(y) = x*tau(x) - y*tau(y), 1<=x<=y<=n.

1, 2, 4, 5, 7, 8, 9, 10, 11, 13, 14, 15, 16, 18, 21, 22, 23, 24, 25, 26, 29, 30, 31, 32, 33, 34, 36, 37, 38, 39, 40, 42, 43, 45, 47, 48, 49, 50, 52, 53, 54, 55, 56, 57, 58, 60, 61, 62, 63, 65, 67, 69, 70, 71, 73, 74, 75, 76, 77, 78, 79, 80, 83, 84, 85, 86, 87, 91, 92, 94, 95

Offset

1,2

Links

Table of n, a(n) for n=1..71.

Prog

(PARI) for(n=1, 130, print1(sum(i=1, n, sum(j=1, i, if(prime(i)-prime(j)-i*numdiv(i)+j*numdiv(j), 0, 1))), ", "))

Crossrefs

Cf. A000005.

Sequence in context: A000394 A039184 A039137 * A074232 A007417 A039099

Adjacent sequences: A071804 A071805 A071806 * A071808 A071809 A071810

Keyword

nonn

Author

Benoit Cloitre, Jun 06 2002

Status

approved