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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. +0
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 (list; graph; listen)
OFFSET

1,2

COMMENT

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: A093505 A112823 A074399 this_sequence A093074 A007917 A136548

Adjacent sequences: A090299 A090300 A090301 this_sequence A090303 A090304 A090305

KEYWORD

nonn

AUTHOR

Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Nov 30 2003

EXTENSIONS

More terms from Frank Ellermann, Dec 03, 2003

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Last modified September 6 16:04 EDT 2008. Contains 143483 sequences.


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