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A128491 Primes in A128490. 1
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 (list; graph; refs; listen; history; text; internal format)
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

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Last modified August 13 19:30 EDT 2020. Contains 336451 sequences. (Running on oeis4.)