A175487 a(n) = smallest prime > a(n-1) such that (a(n-1)+a(n)) is a multiple of nextprime(a(n-1)).

2, 7, 37, 127, 397, 3613, 18089, 162881, 1791787, 41211197, 370900973, 4821712733, 43395414737, 477349562419, 4296146062051, 227695741289567, 9335525392876531, 326743388750679161, 16663912826284638251

Offset

1,1

Comments

Next 10 terms: 583236948919962339073, 9915028131639359764313,

406516153397213750338933,24797485357230038770679749,

223177368215070348936118621,5579434205376758723402966617,

295710012884968212340357231241,23361091017912488774888221274279,

1518470916164311770367734382831699,56183423898079535503606172164775599.

Links

Table of n, a(n) for n=1..19.

Example

a(1)=2; a(2)=7 because 2+7=9 is a multiple of 3=nextprime(2)
a(3)=37 because 7+37=44 is a multiple of 11=nextprime(7)
37+127=164=4*41 (41=nextprime(37))
127+397=524=4*131 (131=nextprime(127)
397+3613=4010=10*401 (401=nextprime(397))
3613+18089=21702=6*3617 (3617=nextprime(3613))
18089+162881=180970=10*18097 (18097=nextprime(18089))
162881+1791787=1954668=12*162889 (162889=nextprime(162881))
1791787+41211197=43002984=24*1791791 (1791791=nextprime(1791787)).

Mathematica

<<NumberTheory`NumberTheoryFunctions`; a=2; np=NextPrime[a]; s={a};
Do[Do[If[PrimeQ[p=np*k-a], AppendTo[s, p]; a=p; np=NextPrime[a]; Break[]], {k, 1000}], {30}]; s

Crossrefs

Cf. A178468.

Sequence in context: A029990 A042465 A041051 * A216362 A002787 A062394

Adjacent sequences: A175484 A175485 A175486 * A175488 A175489 A175490

Keyword

nonn

Author

Zak Seidov, May 28 2010

Status

approved