A093321 - OEIS

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A093321

a(1) = 1; for m >= 2, a(m) =sum_{primes p<m which do not divide m} a(pi(p)), where pi(p) is the order of p among the primes = the number of primes <= p.

1, 0, 1, 0, 1, 1, 2, 1, 2, 0, 2, 2, 3, 3, 3, 3, 4, 5, 6, 5, 7, 5, 7, 8, 8, 7, 9, 8, 9, 7, 9, 10, 10, 8, 10, 10, 11, 11, 12, 11, 13, 15, 16, 17, 18, 16, 19, 21, 22, 20, 20, 20, 22, 24, 23, 24, 24, 24, 25, 27, 29, 31, 34, 33, 32, 32, 34, 37, 38, 38, 40, 44, 45, 49, 51, 50, 51, 50, 52, 55

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OFFSET

1,7

LINKS

Table of n, a(n) for n=1..80.

MATHEMATICA

PrimeFactors[n_Integer] := Flatten[ Table[ # [[1]], {1}] & /@ FactorInteger[n]]; a[1] = 1; a[n_] := a[n] = (Plus @@ (a[ # ] & /@ Complement[ Range[ PrimePi[n]], PrimePi[ PrimeFactors[n]]])); Table[ a[n], {n, 80}] (* Robert G. Wilson v, May 04 2004 *)

CROSSREFS

Cf. A093320, A094163.

Sequence in context: A325033 A333626 A117448 * A302015 A046144 A335904

Adjacent sequences: A093318 A093319 A093320 * A093322 A093323 A093324

KEYWORD

nonn,easy

AUTHOR

Leroy Quet, Apr 26 2004

EXTENSIONS

More terms from Robert G. Wilson v, May 04 2004

STATUS

approved