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A286190
Smallest k such that sopf(k) >= sopf(k+1) >= ... >= sopf(k+n), where sopf = A008472.
1
3, 13, 13, 491, 1516, 12721, 12721, 109453, 1473257, 120797465, 624141002, 4044619541, 136797949237, 315400191511, 1285600699441
OFFSET
1,1
COMMENTS
Here sopf(k) is the sum of the distinct primes dividing k (A008472).
a(16) > 10^13.
EXAMPLE
sopf(13) = 13, sopf(14) = 9, sopf(15) = 8, sopf(16) = 2. This is the first run of 4 nonincreasing values, so a(3) = 13.
MATHEMATICA
sopf[n_] := If[n == 1, 0, Total[First /@ FactorInteger@n]]; s = Array[ sopf, 120000]; Table[ SelectFirst[ Range[ Length@s - n], Sort[t = Take[s, {#, # + n}]] == Reverse[t] &], {n, 8}]
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Giovanni Resta, May 04 2017
STATUS
approved