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A114228 Smallest number m such that prime(n)+2*prime(m) is a prime. 8
1, 2, 1, 2, 1, 2, 1, 2, 4, 2, 1, 2, 1, 2, 2, 4, 2, 1, 6, 2, 1, 2, 4, 1, 2, 1, 2, 1, 4, 1, 2, 4, 3, 4, 2, 2, 1, 2, 2, 4, 3, 2, 1, 4, 7, 5, 1, 2, 1, 2, 8, 3, 2, 2, 2, 4, 2, 1, 6, 3, 4, 1, 2, 1, 4, 2, 3, 2, 1, 2, 4, 2, 2, 1, 2, 12, 1, 8, 3, 4, 3, 6, 2, 1, 2, 4, 1, 2, 1, 12, 11, 1, 14, 1, 2, 4, 6, 7, 2, 3, 2, 2, 8 (list; graph; refs; listen; history; text; internal format)
OFFSET

2,2

COMMENTS

a(A114229(n)) = n for n >=1 and a(m) <> n for m < A114229(n). - Reinhard Zumkeller, Oct 31 2013

LINKS

Reinhard Zumkeller, Table of n, a(n) for n = 2..10000

EXAMPLE

prime(2)=3, 3+2*prime(1)=7 is prime, so a(2)=1;

prime(3)=5, 5+2*prime(2)=11 is prime, so a(3)=2;

...

prime(20)=71, 71+2*prime(6)=97 is prime, so a(20)=6.

MATHEMATICA

Table[p1 = Prime[n1]; n2 = 1; p2 = 2; While[ cp = p1 + 2*p2; ! PrimeQ[cp], n2++; p2 = Prime[n2]]; n2, {n1, 2, 201}]

PROG

(Haskell)

a114228 n = head [m | m <- [1..],

                      a010051 (a000040 n + 2 * a000040 m) == 1]

-- Reinhard Zumkeller, Oct 31 2013

CROSSREFS

Cf. A114227.

Cf. A010051, A000040.

Sequence in context: A030738 A341541 A330559 * A230287 A336336 A168580

Adjacent sequences:  A114225 A114226 A114227 * A114229 A114230 A114231

KEYWORD

easy,nonn

AUTHOR

Lei Zhou, Nov 18 2005

STATUS

approved

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Last modified June 25 00:34 EDT 2021. Contains 345445 sequences. (Running on oeis4.)