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A085107 Starting with n-1 go on adding the numbers less than n and coprime to it in descending order until one gets a prime. a(n) = this prime, or 0 if no such number exists. 1
0, 0, 2, 3, 7, 5, 11, 7, 0, 19, 19, 11, 23, 13, 53, 0, 31, 17, 0, 19, 0, 101, 43, 23, 47, 131, 0, 139, 0, 29, 59, 31, 233, 223, 67, 179, 71, 37, 373, 109, 79, 41, 83, 43, 269, 457, 0, 47, 431, 139, 641, 313, 103, 53, 107, 251, 613, 643, 0, 59, 0, 61, 587, 0, 127, 521, 131, 67 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

a(p+1) = p, p is a prime.

If n is prime and 2n-3 is not prime, then a(n) = 0. - David Wasserman, Jan 27 2005

There are 105 zeros in the first 1000 terms. - Harvey P. Dale, Feb 24 2016

LINKS

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

EXAMPLE

a(10) = 9 + 7 + 3 = 19.

MATHEMATICA

cp[n_]:=SelectFirst[Accumulate[Select[Range[n, 1, -1], CoprimeQ[ #, n]&]], PrimeQ]/._Missing->0; Array[cp, 70] (* The program uses the SelectFirst function from Mathematica version 10 *) (* Harvey P. Dale, Feb 24 2016 *)

CROSSREFS

Sequence in context: A045790 A085102 A087572 * A241082 A219789 A034694

Adjacent sequences:  A085104 A085105 A085106 * A085108 A085109 A085110

KEYWORD

nonn

AUTHOR

Amarnath Murthy and Meenakshi Srikanth (menakan_s(AT)yahoo.com), Jul 04 2003

EXTENSIONS

More terms from David Wasserman, Jan 27 2005

STATUS

approved

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Last modified December 3 08:48 EST 2016. Contains 278698 sequences.