A114264 n(k) is the minimum number that require at least k to make Prime[n]+2*Prime[n+k] a prime.

2, 10, 9, 7, 8, 40, 80, 28, 34, 73, 52, 174, 86, 105, 127, 161, 326, 225, 356, 154, 245, 394, 362, 350, 279, 586, 846, 321, 929, 1822, 1683, 1208, 1091, 2025, 947, 2108, 1361, 3181, 372, 2774, 1898, 3785, 3676, 2194, 6447, 2919, 3590, 7092, 4955, 2474, 19409

Offset

1,1

Links

Table of n, a(n) for n=1..51.

Example

Prime[2]+2*Prime[2+1]=3+2*5=13 is prime, so n(1)=2;
Prime[3]+2*Prime[3+1]=5+2*7=19 is prime, not counted;
...
Prime[7]+2*Prime[7+4]=17+2*31=79 is prime, so n(4)=7;

Mathematica

Do[n[k] = 0, {k, 1, 2000}]; ct = 0; nm = 0; n2 = 0; n1 = 2; p1 = 3; While[ct < 200, n2 = 1; p2 = Prime[n1 + n2]; While[cp = p1 + 2*p2; ! PrimeQ[cp], n2++; p2 = Prime[n1 + n2]]; If[n[n2] == 0, n[n2] = n1; If[n2 > nm, nm = n2]; If[n2 <= 200, ct++ ]; Print[Table[n[k], {k, 1, nm}]]]; n1++; p1 = Prime[n1]]

Crossrefs

Cf. A114227, A114230, A073703, A114235, A114262, A114229, A114232, A114234, A114237, A114263.

Sequence in context: A227716 A033839 A196367 * A081100 A215463 A066556

Adjacent sequences: A114261 A114262 A114263 * A114265 A114266 A114267

Keyword

nonn

Author

Lei Zhou, Nov 20 2005

Status

approved