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A126807
Numbers k such that A014138(k+1) (the partial sum of the first k Catalan numbers, starting 1, 2, 5, ...) is a prime.
0
1, 8, 10, 30, 45, 145, 794, 2772, 2787
OFFSET
1,2
MAPLE
s[0]:=1: for n to 1000 do s[n]:= s[n-1]+binomial(2*n+2, n+1)/(n+2) end do: a:= proc (n) if isprime(s[n]) = true then n else end if end proc: seq(a(n), n= 0.. 1000); # Emeric Deutsch, Aug 28 2007
MATHEMATICA
s = 0; Do[s = s + (2n)!/n!/(n+1)!; If[ PrimeQ[s], Print[n-1]], {n, 200}]
CROSSREFS
Cf. A014137, A121852 (sum of first k Catalan numbers A014137(k) is prime).
Sequence in context: A108940 A007939 A212767 * A230110 A223587 A302312
KEYWORD
more,nonn
AUTHOR
Alexander Adamchuk, Feb 23 2007
EXTENSIONS
3 more terms from Emeric Deutsch, Aug 28 2007
Name clarified by Jon E. Schoenfield, Mar 25 2019
STATUS
approved