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 A231885 Primes of the form Catalan(n) - 1. 4
 13, 41, 131, 1429, 4861, 477638699, 4861946401451, 5632681584560312734993915705849145099, 16435314834665426797069144960762886143367590394939, 171069509209912116706646841207804116182333282333996796075729541331934805254423 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS The 22nd term a(22) in the sequence has 862 digits. a(23) has 1134 digits; a(25) has 1413 digits; a(30) has 2046 digits; a(31) has 2348 digits (these are not included in b-file). LINKS K. D. Bajpai, Table of n, a(n) for n = 1..22 EXAMPLE a(2)= 41: n= 5: (2*n)!/(n!*(n + 1)!)-1= 41 which is prime. a(4)= 1429: n= 8: (2*n)!/(n!*(n + 1)!)-1= 1429 which is prime. MAPLE KD:= proc() local a; a:= (2*n)!/(n!*(n + 1)!)-1; if isprime(a) then return(a): fi; end: seq(KD(), n=1..150); MATHEMATICA Select[CatalanNumber[Range]-1, PrimeQ] (* Harvey P. Dale, Dec 21 2019 *) CROSSREFS Cf. A000108 (Catalan numbers). Cf. A053427 (numbers n : Catalan(n)-1 is prime). Cf. A053429 (numbers n such that Catalan(n)+1 is prime). Cf. A230061 (primes of the form Catalan(n)+1). Sequence in context: A141970 A305155 A355965 * A167240 A147247 A028468 Adjacent sequences: A231882 A231883 A231884 * A231886 A231887 A231888 KEYWORD nonn AUTHOR K. D. Bajpai, Nov 21 2013 STATUS approved

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Last modified October 2 13:28 EDT 2023. Contains 365833 sequences. (Running on oeis4.)