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A071805 Number of pairs (x,y) such that prime(x) + prime(y) = x*tau(x) + y*tau(y), 1<=x<=y<=n. 0
0, 1, 2, 2, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 5, 5, 5, 5, 6, 6, 6, 6, 6, 6, 6, 8, 9, 10, 10, 10, 13, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 20, 20, 22, 22, 22, 22, 23, 23, 23, 23, 23, 23 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

LINKS

Table of n, a(n) for n=1..80.

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: A302437 A179932 A267649 * A063511 A334789 A283207

Adjacent sequences:  A071802 A071803 A071804 * A071806 A071807 A071808

KEYWORD

nonn

AUTHOR

Benoit Cloitre, Jun 06 2002

STATUS

approved

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Last modified June 2 08:23 EDT 2020. Contains 334767 sequences. (Running on oeis4.)