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A344781 Numbers k such that A070313(k) = 2^k - (2*k+1) is a prime number. 0
4, 7, 8, 28, 32, 81, 669, 1108, 1699, 1839, 2319, 9566, 14866, 30855, 35932 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

The corresponding primes are 7, 113, 239, 268435399, 4294967231, 2417851639229258349412189, ...

If k is a term of this sequence then 2^(k-1)*(2^k-(2*k+1)) is a term of A056075 (see Farideh Firoozbakht's comment in A056075).

LINKS

Table of n, a(n) for n=1..15.

EXAMPLE

4 is a term since 2^4 - (2*4+1) = 16 - 9 = 7 is a prime.

7 is a term since 2^7 - (2*7+1) = 128 - 15 = 113 is a prime.

MATHEMATICA

Select[Range[2400], PrimeQ[2^# - 2*# - 1] &]

CROSSREFS

Cf. A056075, A070313.

Sequence in context: A295325 A239290 A057464 * A160629 A093105 A141669

Adjacent sequences:  A344778 A344779 A344780 * A344782 A344783 A344784

KEYWORD

nonn,more

AUTHOR

Amiram Eldar, May 28 2021

STATUS

approved

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Last modified December 4 02:40 EST 2021. Contains 349469 sequences. (Running on oeis4.)