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A128490 Let p(k) denote the k-th prime. Sequence gives integers of the form [p(n+1)*p(n) - 1]/[p(n+1)-p(n)]. 1
5, 7, 17, 19, 55, 71, 109, 111, 161, 191, 379, 415, 449, 505, 521, 681, 881, 961, 1025, 1079, 1189, 1231, 1639, 1799, 2071, 2449, 2591, 2755, 2991, 3079, 3457, 3499, 3921, 3951, 4159, 4265, 4815, 5161, 5201, 5831, 6049, 6425, 6805, 9281, 9505, 9521, 10751 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..47.

EXAMPLE

[5*3-1]/(5-2) = 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 print(j); fi; od; end: P(1000);

CROSSREFS

Cf. A128491.

Sequence in context: A075304 A168245 A242929 * A023519 A023517 A128491

Adjacent sequences:  A128487 A128488 A128489 * A128491 A128492 A128493

KEYWORD

easy,nonn

AUTHOR

Paolo P. Lava and Giorgio Balzarotti, Mar 05 2007

STATUS

approved

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Last modified August 12 16:40 EDT 2020. Contains 336439 sequences. (Running on oeis4.)