A090302 Begin with n and consider numbers obtained by successively subtracting 0, 1, 2, 3, ...; a(n) = largest prime that arises in the process, i.e., largest prime of the form n - T(r), where T(r) is the r-th triangular number; or 0 if no such number exists.

0, 2, 3, 3, 5, 5, 7, 7, 3, 7, 11, 11, 13, 13, 5, 13, 17, 17, 19, 19, 11, 19, 23, 23, 19, 23, 17, 13, 29, 29, 31, 31, 23, 31, 29, 0, 37, 37, 29, 37, 41, 41, 43, 43, 17, 43, 47, 47, 43, 47, 41, 37, 53, 53, 19, 53, 47, 43, 59, 59, 61, 61, 53, 61, 59, 11, 67, 67, 59, 67, 71

Offset

1,2

Comments

a(p) = p if p is a prime.

Links

T. D. Noe, Table of n, a(n) for n = 1..10000

Formula

Largest prime of the form n - r(r+1)/2.

Crossrefs

Cf. A076768 (positions of 0's).

Cf. A132399.

Sequence in context: A342693 A349338 A074399 * A093074 A284412 A136548

Adjacent sequences: A090299 A090300 A090301 * A090303 A090304 A090305

Keyword

nonn

Author

Amarnath Murthy, Nov 30 2003

Extensions

More terms from Frank Ellermann, Dec 03 2003

Status

approved