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A286190 Smallest k such that sopf(k) >= sopf(k+1) >= ... >= sopf(k+n), where sopf = A008472. 1

%I

%S 3,13,13,491,1516,12721,12721,109453,1473257,120797465,624141002,

%T 4044619541,136797949237,315400191511,1285600699441

%N Smallest k such that sopf(k) >= sopf(k+1) >= ... >= sopf(k+n), where sopf = A008472.

%C Here sopf(k) is the sum of the distinct primes dividing k (A008472).

%C a(16) > 10^13.

%e sopf(13) = 13, sopf(14) = 9, sopf(15) = 8, sopf(16) = 2. This is the first run of 4 nonincreasing values, so a(4) = 13.

%t 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}]

%Y Cf A008472, A189882.

%K nonn,more

%O 1,1

%A _Giovanni Resta_, May 04 2017

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Last modified May 27 21:14 EDT 2022. Contains 354110 sequences. (Running on oeis4.)