A090468 Class 13+ primes.

545587687, 852480757, 1048438561, 1150849009, 1323457987, 1745980517, 1756123441, 1785398401, 1798736161, 1892507347, 1937020021, 2002155601, 2136716521, 2150905573, 2229004913, 2548101601, 2671514917, 2838761021, 2861623537, 2864335361, 2905705507, 2908486561, 2972006551

Offset

1,1

References

R. K. Guy, Unsolved Problems in Number Theory, A18.

Links

David A. Corneth, Table of n, a(n) for n = 1..10000 (first 850 terms from M. F. Hasler)

Example

1048438561 is in the sequence as it is a Class 13+ prime via 1048438561, 524219281, 262109641, 131054821, 65527411, 16381853, 910103, 2917, 1459, 73, 37, 19, 2. - David A. Corneth, May 24 2026

Maple

# For Maple program see Mathar link in A005105.

Mathematica

PrimeFactors[n_Integer] := Flatten[ Table[ #[[1]], {1}] & /@ FactorInteger[n]]; f[n_Integer] := Block[{m = n}, If[m == 0, m = 1, While[ IntegerQ[m/2], m /= 2]; While[ IntegerQ[m/3], m /= 3]]; Apply[Times, PrimeFactors[m] + 1]]; ClassPlusNbr[n_] := Length[ NestWhileList[f, n, UnsameQ, All]] - 3; Prime[ Select[ Range[195000000], ClassPlusNbr[ Prime[ # ]] == 13 &]]

Crossrefs

Cf. A005113, A005105 - A005108, A081633 - A081639, A084071, A129474.

Sequence in context: A204779 A278201 A172619 * A214480 A251441 A350136

Adjacent sequences: A090465 A090466 A090467 * A090469 A090470 A090471

Keyword

nonn

Author

Robert G. Wilson v, Nov 26 2003

Status

approved