21445

Appears in sequences

• Numbers k such that 15*2^k + 1 is prime.at n=31A002258
• Numbers whose concatenation of prime factors (with multiplicity) is a square.at n=40A038693
• Numbers k such that 100k+1, 100k+3, 100k+7, 100k+9 are all primes.at n=31A064687
• Expansion of Product_{k > 0} (1 + A147665(k)*x^k).at n=30A147871
• Number of Dyck paths of semilength n avoiding the pattern U^4 D^4 U D.at n=23A225691
• Number of 3 X n 0..2 arrays with horizontal differences mod 3 never 1, vertical differences mod 3 never -1, and rows and columns lexicographically nondecreasing.at n=39A229446
• Reduced numerators of the Kirchhoff sum index for the n-halved cube graph.at n=7A290367
• Numbers k such that A339549(k) = A339549(k+1).at n=20A339550