A108769 Numbers m such that m^2 + (m+1)^2 is a semiprime.

3, 6, 8, 10, 11, 13, 15, 16, 18, 20, 26, 27, 31, 33, 37, 38, 40, 43, 44, 45, 48, 51, 52, 54, 55, 56, 57, 59, 62, 63, 64, 67, 68, 73, 74, 75, 76, 77, 80, 81, 83, 89, 92, 94, 98, 105, 107, 111, 112, 113, 114, 117, 120, 123, 124, 129, 131, 133, 134, 138, 140, 141, 142, 143

Offset

1,1

Comments

Numbers m such that A099776(m) is a semiprime. - Michel Marcus, Nov 17 2022

Links

Alois P. Heinz, Table of n, a(n) for n = 1..65536

Maple

a:= proc(n) local k; for k from 1+`if`(n=1, 0, a(n-1))
      while (t-> isprime(t) or numtheory[bigomega](t)
      >2)(2*k*(k+1)+1) do od: k
    end:
seq(a(n), n=1..70);  # Alois P. Heinz, Aug 01 2019

Mathematica

Select[Range[1000], PrimeOmega[#^2 + (#+1)^2] == 2&] (* Jean-François Alcover, Nov 17 2022 *)

Prog

(PARI) isok(m) = bigomega(m^2 + (m+1)^2) == 2; \\ Michel Marcus, Nov 17 2022

Crossrefs

Cf. A001358, A027861, A099776.

Sequence in context: A055073 A328505 A012132 * A286754 A186387 A258050

Adjacent sequences: A108766 A108767 A108768 * A108770 A108771 A108772

Keyword

easy,nonn

Author

Jason Earls, Jun 25 2005

Status

approved