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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.
2
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.
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
KEYWORD
nonn
AUTHOR
Amarnath Murthy, Nov 30 2003
EXTENSIONS
More terms from Frank Ellermann, Dec 03 2003
STATUS
approved