A266451 Semiprimes that are the sum of six consecutive semiprimes.

58, 91, 123, 142, 161, 205, 278, 473, 566, 614, 706, 718, 802, 838, 851, 889, 1079, 1211, 1226, 1238, 1262, 1286, 1385, 1415, 1633, 1714, 1819, 1891, 1945, 2005, 2123, 2147, 2194, 2217, 2327, 2374, 2427, 2563, 2594, 2653, 2771, 2815, 2854, 2947, 2987, 3118, 3133, 3151, 3199, 3214, 3305, 3379

Offset

1,1

Links

Robert Israel, Table of n, a(n) for n = 1..10000

Example

58 = A001358(21) = A001358(1) + ... + A001358(6) = 4+6+9+10+14+15,
91 = A001358(31) = A001358(3) + ... + A001358(8) = 9+10+14+15+21+22.

Maple

N:= 10^4: # to get all terms where the 6 consecutive semiprimes <= N
P:= select(isprime, [2, seq(i, i=3..N/2, 2)]): nP:= nops(P):
SP:= NULL:
for i from 1 to nP do
  for j from 1 to nP while P[i]*P[j] <= N do od:
  SP:= SP, op(map(`*`, P[i], P[1..j-1]));
od:
SP:= sort(convert({SP}, list)): nSP:= nops(SP):
select(numtheory:-bigomega=2, [seq(convert(SP[i..i+5], `+`), i=1..nSP-5)]): # Robert Israel, Nov 19 2017

Mathematica

Select[(Total[#] & /@ Partition[Select[Range[4, 9999], 2 == PrimeOmega[#] &], 6, 1]), 2 == PrimeOmega[#] &]

Crossrefs

Cf. A001358, A092192, A131610, A158339, A254712.

Sequence in context: A039430 A043253 A044033 * A124680 A354448 A181462

Adjacent sequences: A266448 A266449 A266450 * A266452 A266453 A266454

Keyword

nonn

Author

Zak Seidov, Dec 29 2015

Status

approved