A260966 a(0)=1, then a(n) is the least sum of two successive primes that is a multiple of n and > a(n-1).

1, 5, 8, 12, 24, 30, 36, 42, 112, 144, 210, 308, 360, 390, 434, 450, 480, 918, 990, 1064, 1120, 1428, 1518, 1656, 1848, 1900, 2132, 2430, 2604, 2610, 2640, 2728, 2912, 2970, 2992, 3010, 3240, 3330, 3952, 4056, 4680, 5740, 6090, 6450, 6600, 6660, 6762, 7990, 8256, 8428, 9000, 9282, 9308

Offset

0,2

Links

Robert Israel, Table of n, a(n) for n = 0..4628

Example

a(1)=5=2+3, a(2)=8=3+5, a(3)=12=5+7, a(4)=24=11+13, a(5)=30=13+17.

Maple

N:= 10^5: # get all terms using primes <= N
Primes:= select(isprime, [2, (2*i+1 $ i=1..floor((N-1)/2))]):
Sprimes:= Primes[1..-2] + Primes[2..-1]:
A[0]:= 1: x[0]:= 0: ok:= true:
for n from 1 while ok do
  ok:= false;
  for t from x[n-1]+1 to nops(Sprimes) do
    if Sprimes[t] mod n = 0 then
      A[n]:= Sprimes[t]; x[n]:= t; ok:= true; break
    fi
  od
od:
seq(A[i], i=0..n-2); # Robert Israel, Aug 06 2015

Mathematica

Prepend[Reap[n=1; Do[If[Mod[(a=Prime[k]+Prime[k+1]), n]<1, Sow[a]; i++], {k, 1000}]][[2, 1]], 1]
nxt[{n_, a_}]:=Module[{sprs=Total/@Partition[Prime[Range[1000]], 2, 1]}, {n+1, SelectFirst[sprs, Divisible[#, n+1]&&#>a&]}]; Transpose[ NestList[ nxt, {0, 1}, 60]][[2]] (* Harvey P. Dale, Jun 02 2016 *)

Crossrefs

Cf. A001043, A247245.

Sequence in context: A314419 A138051 A026279 * A338547 A124434 A180930

Adjacent sequences: A260963 A260964 A260965 * A260967 A260968 A260969

Keyword

nonn

Author

Zak Seidov, Aug 06 2015

Status

approved