A076471 - OEIS

A076471

Number of pairs (p,q) of successive primes with p+q<=n.

0, 0, 0, 0, 1, 1, 1, 2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 4, 4, 4, 4, 4, 4, 5, 5, 5, 5, 5, 5, 6, 6, 6, 6, 6, 6, 7, 7, 7, 7, 7, 7, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 9, 9, 9, 9, 9, 9, 9, 9, 10, 10, 10, 10, 10, 10, 10, 10, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 12, 12, 12, 12, 12, 12, 13, 13, 13, 13, 13, 13

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OFFSET

1,8

COMMENTS

A056172(n)-1 <= a(n) <= A056172(n);

a(n) = A076472(n) + A076473(n).

LINKS

Table of n, a(n) for n=1..89.

EXAMPLE

Pairs (p,q) of successive primes with p+q<=27: {(2,3), (3,5), (5,7), (7,11), (11,13)}, hence a(27)=5.

MATHEMATICA

With[{t=Total/@Partition[Prime[Range[100]], 2, 1]}, Table[Count[t, _?(#<=n&)], {n, 100}]] (* Harvey P. Dale, Apr 16 2015 *)