A037231 Primes which set a new record for length of Pratt certificate.

2, 3, 7, 23, 43, 139, 283, 659, 1319, 5179, 9227, 23159, 55399, 148439, 366683, 793439, 1953839, 4875119, 9750239, 27353747, 71815607, 192287243, 430893643

Offset

1,1

Links

Table of n, a(n) for n=1..23.

Eric Weisstein's World of Mathematics, Pratt Certificate.

Mathematica

a[1] = 1; a[n_] := a[n] = 1 + Plus @@ (a@ PrimePi@ # & /@ First /@ FactorInteger[ Prime@ n - 1]); t = Table[ 0, {25}]; k = 2; While[k < 23420001, b = a[k]/2; If[b < 1001 && t[[b]] == 0, t[[b]] = Prime@ k; Print[{b, Prime@ k }]]; k++]; t

Crossrefs

Cf. A037202.

Sequence in context: A106865 A267504 A000057 * A376188 A248525 A366929

Adjacent sequences: A037228 A037229 A037230 * A037232 A037233 A037234

Keyword

nonn,more,changed

Author

David W. Wilson

Status

approved