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Search: id:A100549
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| A100549 |
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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. |
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6
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| 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; listen)
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OFFSET
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1,2
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LINKS
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David Applegate and N. J. A. Sloane, Table of n, a(n) for n = 1..10000
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EXAMPLE
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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.
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MAPLE
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# 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;
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CROSSREFS
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Cf. A100762, A100417, A141586, A082725.
Sequence in context: A104517 A098397 A082091 this_sequence A085962 A160821 A060244
Adjacent sequences: A100546 A100547 A100548 this_sequence A100550 A100551 A100552
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KEYWORD
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nonn
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AUTHOR
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David Applegate and N. J. A. Sloane (njas(AT)research.att.com), Sep 15 2008
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