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Sum of the primes from smallest prime factor of n to the largest prime factor of n = largest difference between consecutive divisors of n (ordered by size).
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%I #13 Dec 15 2017 17:36:01

%S 4,20,1278,1339,11074308238,19096347067

%N Sum of the primes from smallest prime factor of n to the largest prime factor of n = largest difference between consecutive divisors of n (ordered by size).

%C 10^11 < a(7) <= 8912510129422438. - _Giovanni Resta_, May 13 2016

%t Select[Range[2, 2000], (p = First /@ FactorInteger[#]; #-#/p[[1]] == Sum[ Prime[i], {i, PrimePi@ p[[1]], PrimePi@ p[[-1]]}]) &] (* _Giovanni Resta_, May 13 2016 *)

%o (PARI) isok(n) = {pf = factor(n)[,1]; my(pmin = vecmin(pf)); s = 0; forprime(p = pmin, vecmax(pf), s += p); s == n - n/pmin;} \\ _Michel Marcus_, Feb 03 2014

%Y Cf. A060681, A074036, A055233, A055514.

%K more,nonn

%O 1,1

%A _Jason Earls_, Sep 19 2002

%E a(5)-a(6) from _Giovanni Resta_, May 13 2016