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A114233 Smallest number m such that 2*prime(n) + prime(m) is a prime. 5
2, 2, 4, 2, 2, 2, 4, 2, 3, 3, 4, 2, 2, 2, 6, 3, 2, 4, 2, 3, 4, 2, 2, 11, 3, 6, 3, 2, 2, 4, 2, 2, 6, 3, 2, 3, 2, 2, 11, 3, 4, 2, 2, 2, 5, 2, 2, 2, 6, 6, 3, 4, 4, 11, 2, 3, 2, 4, 2, 4, 2, 8, 3, 4, 5, 2, 4, 2, 2, 14, 3, 3, 2, 2, 8, 2, 4, 2, 8, 5, 8, 5, 2, 14, 6, 3, 4, 2, 2, 6, 2, 11, 5, 2, 2, 4, 2, 3, 2, 2, 2, 6, 5 (list; graph; refs; listen; history; text; internal format)
OFFSET

3,1

LINKS

Reinhard Zumkeller, Table of n, a(n) for n = 3..10000

EXAMPLE

n=3: 2*prime(3)+prime(2)=2*5+3=13 is prime, so a(3)=2;

n=4: 2*prime(4)+prime(2)=2*7+3=17 is prime, so a(4)=2;

n=5: 2*prime(5)+prime(2)=2*11+3=25 is not prime

...

2*prime(5)+prime(4)=2*11+7=29 is prime, so a(5)=4.

MATHEMATICA

Table[p1 = Prime[n1]; n2 = 1; p2 = Prime[n2]; While[cp = 2*p1 + p2; ! PrimeQ[cp], n2++; If[n2 >= n1, Print[n1]]; p2 = Prime[n2]]; n2, { n1, 3, 202}]

snm[n_]:=Module[{m=1, p=2Prime[n]}, While[!PrimeQ[p+Prime[m]], m++]; m]; Array[ snm, 110, 3] (* Harvey P. Dale, Sep 30 2017 *)

PROG

(Haskell)

a114233 n = head [m | m <- [1 .. n],

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

-- Reinhard Zumkeller, Oct 31 2013

CROSSREFS

Cf. A073703, A114227, A114228, A114231.

Cf. A010051, A000040.

Sequence in context: A092188 A097884 A094818 * A279047 A063086 A077636

Adjacent sequences:  A114230 A114231 A114232 * A114234 A114235 A114236

KEYWORD

easy,nonn

AUTHOR

Lei Zhou, Nov 20 2005

EXTENSIONS

Edited definition to conform to OEIS style. - Reinhard Zumkeller, Oct 31 2013

STATUS

approved

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Last modified May 24 15:25 EDT 2019. Contains 323532 sequences. (Running on oeis4.)