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A156311 Number of ways to write prime(n) = prime(k) + prime(k+1)*m. 4
0, 0, 1, 0, 1, 1, 1, 1, 2, 2, 0, 1, 1, 1, 3, 2, 1, 1, 0, 1, 2, 0, 2, 3, 0, 1, 2, 1, 0, 2, 1, 3, 2, 2, 2, 0, 1, 1, 2, 3, 2, 1, 1, 2, 2, 0, 0, 1, 2, 1, 2, 1, 0, 2, 2, 2, 1, 3, 1, 1, 4, 3, 1, 1, 3, 2, 0, 1, 1, 1, 3, 3, 1, 1, 0, 3, 3, 2, 4, 0, 2, 1, 1, 2, 2, 2, 1, 0, 1, 3, 2, 3, 1, 2, 0, 2, 3, 1, 3, 1, 2, 5, 3, 1, 1 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,9

COMMENTS

a(n) = #{k: prime(n) mod prime(k+1) = prime(k)};

a(A049084(A156312(n)))>0; a(A049084(A156313(n)))=0;

a(A049084(A156314(n)))=n and a(m)<n for m < A049084(A156314(n)).

LINKS

R. Zumkeller, Table of n, a(n) for n = 1..10000

EXAMPLE

A000040(14)=43: a(14) = #{3+5*8} = 1;

A000040(15)=47: a(15) = #{2+3*15, 5+7*6, 13+17*2} = 3;

A000040(16)=53: a(16) = #{2+3*17, 3+5*10} = 2.

PROG

(PARI) a(n, t=prime(n))=my(s, p=2); forprime(q=3, nextprime(t/2), if(t%q==p, s++); p=q); s \\ Charles R Greathouse IV, Mar 13 2015

CROSSREFS

Sequence in context: A290531 A206442 A137581 * A270740 A189463 A287451

Adjacent sequences:  A156308 A156309 A156310 * A156312 A156313 A156314

KEYWORD

nonn

AUTHOR

Reinhard Zumkeller, Feb 07 2009

STATUS

approved

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Last modified November 15 11:35 EST 2018. Contains 317238 sequences. (Running on oeis4.)