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A128841 First occurrence of primes that are 2^k greater than the product of lesser twin primes. 0
5, 7, 11, 19, 47, 67, 131, 271, 677, 1039, 2063, 4099, 3343337, 97729, 32771, 65539, 133877, 262147, 524453, 13971970981, 2097317, 4194319, 8388623, 16777381, 36889577, 67108879, 134217893, 268435459, 536952257, 1073741827, 2147483813 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

It is interesting from the example that the first three primes 19,31 and 181 greater than twinl#(n) + 2^4 are all greater twin primes. The next prime is the 1824 digit number twinl#(469) + 2^4 and is not part of a twin prime pair.

LINKS

Table of n, a(n) for n=1..31.

FORMULA

Define twinl#(n)as the product of the first n lesser twin primes. Then if twinl#(n)+2^k, k=1,2,3..., is prime, list it and skip to the next n.

EXAMPLE

for k=4,Twinl#(1) + 2^4 = 19, the first prime (2^4)-th greater than twinl#(1).

PROG

(PARI) twiprimesl2(n, a) = { local(pr, x, y, j); for(a=0, n, for(j=1, n, pr=1; for(x=1, j, pr*=twinl(x); ); y=pr+2^a; if(ispseudoprime(y), print1(y", "); break ) ) ) } twinl(n) = \The n-th lower twin prime { local(c, x); c=0; x=1; while(c<n, if(isprime(prime(x)+2), c++); x++; ); return(prime(x-1)) }

CROSSREFS

Sequence in context: A038881 A190359 A045441 * A057733 A318078 A174332

Adjacent sequences:  A128838 A128839 A128840 * A128842 A128843 A128844

KEYWORD

nonn

AUTHOR

Cino Hilliard, May 08 2007

STATUS

approved

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Last modified November 17 13:33 EST 2019. Contains 329230 sequences. (Running on oeis4.)