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 A100549 Let n = 2^e_2 * 3^e_ * 5^e_ * ... be the prime factorization of n; then a(n) = largest prime <= 1 + max{e_2, e_3, e_5, ...}; a(1) = 1 by convention. 6
 1, 2, 2, 3, 2, 2, 2, 3, 3, 2, 2, 3, 2, 2, 2, 5, 2, 3, 2, 3, 2, 2, 2, 3, 3, 2, 3, 3, 2, 2, 2, 5, 2, 2, 2, 3, 2, 2, 2, 3, 2, 2, 2, 3, 3, 2, 2, 5, 3, 3, 2, 3, 2, 3, 2, 3, 2, 2, 2, 3, 2, 2, 3, 7, 2, 2, 2, 3, 2, 2, 2, 3, 2, 2, 3, 3, 2, 2, 2, 5, 5, 2, 2, 3, 2, 2, 2, 3, 2, 3, 2, 3, 2, 2, 2, 5, 2, 3, 3, 3, 2, 2, 2, 3, 2 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS David Applegate and N. J. A. Sloane, Table of n, a(n) for n = 1..10000 EXAMPLE If n = 8 = 2^3, a(n) = (largest prime <= 3+1) = 3. If n = 480 = 2^5*3*5, a(n) = (largest prime <= 1 + max{5,1,1}) = 5. MAPLE # if n = prod_p p^e_p, then # pp = largest prime <= 1 + max e_p with(numtheory): pp := proc(n) local f, m; option remember; if (n = 1) then return 1; end if; m := 1: for f in op(2..-1, ifactors(n)) do if (f[2] > m) then m := f[2]: end if; end do; prevprime(m+2); end proc; MATHEMATICA {1}~Join~Array[Prime@PrimePi[1 + Max@FactorInteger[#][[All, -1]]] &, 105, 2] (* Michael De Vlieger, Nov 13 2018 *) PROG (PARI) a(n) = if (n==1, 1, precprime(1 + vecmax(factor(n)[, 2]~))); \\ Michel Marcus, Nov 14 2018 CROSSREFS Cf. A100762, A100417, A141586, A082725. Sequence in context: A278744 A082091 A334216 * A085962 A160821 A300225 Adjacent sequences:  A100546 A100547 A100548 * A100550 A100551 A100552 KEYWORD nonn AUTHOR David Applegate and N. J. A. Sloane, Sep 15 2008 STATUS approved

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Last modified June 13 00:57 EDT 2021. Contains 344980 sequences. (Running on oeis4.)