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A122001
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Number of representations of prime p = prime(n) as 2*(p1-p2)+3*p3 (where p1, p2, p3 are primes less than or equal than p), for which p+2*p2(=2*p1+3*p3) is also a prime.
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0
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0, 0, 0, 1, 0, 3, 7, 5, 7, 8, 6, 17, 15, 10, 13, 19, 9, 21, 24, 18, 29, 28, 25, 37, 37, 29, 32, 34, 37, 47, 40, 37, 63, 51, 57, 59, 69, 47, 58, 67, 65, 68, 65, 69, 65, 60, 73, 97, 90, 109, 103, 82, 111, 112, 96, 106, 140
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,6
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EXAMPLE
| a(6)=3 because although 13 (the 6th prime) can be expressed as 2*(p1-p2) + 3*p3 in the following ways:
2*( 2 - 3 ) + 3* 5
2*( 3 - 7 ) + 3* 7
2*( 3 - 13 ) + 3* 11
2*( 5 - 3 ) + 3* 3
2*( 7 - 5 ) + 3* 3
2*( 7 - 11 ) + 3* 7
2*( 13 - 11 ) + 3* 3
only for the three of them (first, fourth and fifth) p+2*p2 is also a prime (19, 19, 23, respectively)
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CROSSREFS
| Cf. A120450, A120451.
Sequence in context: A010624 A019638 A116535 * A161327 A151685 A019809
Adjacent sequences: A121998 A121999 A122000 * A122002 A122003 A122004
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KEYWORD
| nonn
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AUTHOR
| Vassilis Papadimitriou (bpapa(AT)sch.gr), Sep 11 2006
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