A075402 Smallest number such that a(n) + T(n) is a prime, where T(n) is the n-th triangular number.

1, 0, 1, 1, 2, 2, 1, 1, 2, 4, 1, 1, 6, 2, 7, 1, 4, 2, 1, 1, 2, 4, 1, 7, 6, 2, 1, 3, 4, 2, 3, 13, 2, 4, 1, 7, 6, 2, 7, 1, 2, 4, 1, 1, 4, 6, 1, 5, 4, 2, 1, 3, 2, 2, 3, 1, 4, 10, 7, 1, 10, 20, 1, 1, 8, 2, 3, 1, 2, 18, 1, 5, 6, 2, 1, 1, 8, 2, 3, 11, 2, 4, 5, 1, 4, 20, 5, 1, 2, 4, 15, 5, 2, 16, 1, 1, 6, 10, 1

Offset

1,5

Comments

0 occurs only once in this sequence.

Links

Harvey P. Dale, Table of n, a(n) for n = 1..1000

Mathematica

If[PrimeQ[#], #, NextPrime[#]]-#&/@Accumulate[Range[100]] (* Harvey P. Dale, Nov 21 2012 *)

Prog

(PARI) for(n=1, 100, a=n*(n+1)/2:print1(nextprime(a)-a", "))

Crossrefs

Cf. A075403.

Sequence in context: A240168 A199204 A262750 * A276696 A220777 A088855

Adjacent sequences: A075399 A075400 A075401 * A075403 A075404 A075405

Keyword

nonn

Author

Amarnath Murthy, Sep 23 2002

Extensions

Corrected and extended by Ralf Stephan, Mar 19 2003

Status

approved