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URL: https://oeis.org/A221860

⇱ A221860 - OEIS

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A221860
Indices k such that prime(k) - k is a power of 2.
1
1, 2, 3, 15, 39, 2119, 4189897, 5812974437
OFFSET
1,2
COMMENTS
The only primes in this sequence below primepi(10^8) are 2, 3 and 4189897.
prime(5812974437) - 5812974437 = 2^37. - Giovanni Resta, Apr 10 2013
a(9) > 1.4*10^16, if it exists. - Chai Wah Wu, Apr 24 2018
FORMULA
A000040(a(n))-a(n) = 2^floor(log[2](A000040(a(n)))) for all n>1.
PROG
(PARI) n=0; forprime(p=1, 10^8, n++; (t=p-n)==1<<valuation(t, 2)&print1(n", "))
CROSSREFS
Cf. A014689.
Sequence in context: A143880 A037388 A298370 * A216339 A048076 A203432
KEYWORD
nonn,more
AUTHOR
M. F. Hasler, Apr 10 2013
EXTENSIONS
a(8) from Giovanni Resta, Apr 10 2013
STATUS
approved