220992

Appears in sequences

• Numbers k such that 21*2^k+1 is prime.at n=39A032360
• a(n) is the first pentagonal number that is nontrivially the sum of two pentagonal numbers of the type P(p) + P(p+n) (we always have P(k) = P(0) + P(k)).at n=13A133312
• Pentagonal numbers > 0 which are not the difference of two other pentagonal numbers > 0.at n=21A135769
• Pentagonal numbers > 0 which are not the difference of two larger pentagonal numbers.at n=32A136113