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

Author

Amarnath Murthy, Sep 23 2002

Keywords

• nonn

Comments

0 occurs only once in this sequence.

Links

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

Crossrefs

Cf. A075403.

Programs

Mathematica

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

PARI

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

Extensions

Corrected and extended by Ralf Stephan, Mar 19 2003