A128491 Primes in A128490.

5, 7, 17, 19, 71, 109, 191, 379, 449, 521, 881, 1231, 2591, 3079, 3457, 3499, 4159, 9281, 9521, 12511, 13339, 17137, 21121, 23561, 23869, 33151, 39761, 39799, 48619, 53731, 59779, 90281, 104651, 106721, 108991, 148609, 179099, 179999, 189391

Offset

1,1

Links

Table of n, a(n) for n=1..39.

Example

[5*3-1]/[5-3] = 14/2 = 7
[7*5-1]/[7-5] = 34/2 = 17
[11*7-1]/[11-7] = 76/4 = 19

Maple

P:=proc(n) local i, j, k; for i from 1 by 1 to n do j:=(ithprime(i+1)*ithprime(i)-1)/(ithprime(i+1)-ithprime(i)); if j=trunc(j) then if isprime(j) then print(j); fi; fi; od; end: P(1000);

Crossrefs

Cf. A128490.

Sequence in context: A128490 A023519 A023517 * A146949 A048700 A331892

Adjacent sequences: A128488 A128489 A128490 * A128492 A128493 A128494

Keyword

easy,nonn

Author

Paolo P. Lava and Giorgio Balzarotti, Mar 05 2007

Status

approved