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A108769
Numbers m such that m^2 + (m+1)^2 is a semiprime.
2
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
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
KEYWORD
easy,nonn
AUTHOR
Jason Earls, Jun 25 2005
STATUS
approved