A261672 Numbers k such that A037610(k) is prime.

4, 7, 52, 100, 136, 388, 30940, 33250

Offset: 1

Author

Felix Fröhlich, Sep 04 2015

Keywords

• nonn
• more

Comments

The terms are a subset of the terms of A016777, since a term of A037610 can only be prime if it is congruent to 1 modulo 10 and hence congruent to 1 modulo 3. If A037610(k) is congruent to 1 modulo 3, then k is congruent to 1 modulo 3 as well.

No further terms up to 10000.

Examples

			A037610(7) = 1231231 is prime, so 7 is a term of the sequence.
		

Crossrefs

Cf. A037610, A062209.

Programs

Mathematica

Select[Range@ 500, PrimeQ@ Floor[41/333*10^#] &] (* Michael De Vlieger, Sep 07 2015 *)

PARI

a037610(n) = 10^n*41\333
is(n) = ispseudoprime(a037610(n))

Extensions

a(7)-a(8) from Michael S. Branicky, Jun 28 2023