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A224693
Smallest prime p such that p > gpf(p+1) > gpf(p+2) > ... > gpf(p+n) where gpf(m) is the greatest prime factor of m.
0
3, 13, 13, 491, 2011, 12721, 12721, 109453, 586951, 173912393, 785211341, 4044619541, 315400191511, 315400191511
OFFSET
1,1
COMMENTS
a(n) >= A100385(n+1). - Zak Seidov, Apr 17 2013
EXAMPLE
a(4) = 491 because 491 > 41 > 29 > 19 > 11 where:
492 = 2^2*3*41;
493 = 17*29;
494 = 2*13*19;
495 = 3^2*5*11.
MAPLE
with(numtheory):
for n from 1 to 20 do:
ii:=0:
for k from 1 to 10^7 while(ii=0) do:
p:=ithprime(k): it:=0:
for m from 1 to n do:
x0:=factorset(p+m-1):n0:=nops(x0): x1:=factorset(p+m):n1:=nops(x1):
if x0[n0] > x1[n1]
then
it:=it+1:
else
fi:
od:
if it=n
then
printf ( "%d %d \n", n, p):ii:=1:
else
fi:
od:
od:
CROSSREFS
Sequence in context: A076747 A198452 A286190 * A043055 A101235 A230508
KEYWORD
nonn,hard,more
AUTHOR
Michel Lagneau, Apr 15 2013
EXTENSIONS
a(10)-a(12) from Zak Seidov, Apr 17 2013
a(13)-a(14) from Donovan Johnson, Apr 26 2013
STATUS
approved