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Numbers in A075728 which are not one less than some prime.
1

%I #18 Jan 18 2020 20:41:28

%S 120,186,264,450,504,552,696,978,1208,1440,1444,1848,2034,2744,4320,

%T 4410,5376,6888,7020,9264,9968,10944,10989,13952,16080,19152,23160,

%U 29280,31410,34464,38928,39648,49544,56880,60480,67266,73200,78480,82800,91440,102312

%N Numbers in A075728 which are not one less than some prime.

%C The first 30 terms of A075728 are equal to prime(k)-1 for some k. The first term here, n = 120, satisfies |sigma(n) - 2*n| = n. - _Michel Marcus_, Nov 02 2013

%H Donovan Johnson, <a href="/A179232/b179232.txt">Table of n, a(n) for n = 1..1000</a>

%F A075728 \ A006093.

%o (PARI) lista(nn) = {rec = -1; for (n=1, nn, d = abs(sigma(n) - 2*n); if (d > rec, if (! isprime(d+1), print1(d, ", ")); rec = d;););} \\ _Michel Marcus_, Nov 02 2013

%Y Cf. A006093, A075728.

%K nonn

%O 1,1

%A _Artur Jasinski_, Jul 04 2010

%E More terms from _R. J. Mathar_, Jul 05 2010

%E A-number typo corrected by _R. J. Mathar_, Jul 16 2010