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%I #6 Jan 18 2019 13:49:51
%S 5,10,19,27,46,52,70,81,96,128,135,151,186,180,196,218,258,264,270,
%T 339,309,354,350,414,423,433,426,442,496,488,567,588,558,624,638,672,
%U 632,657,732,668,816,882,868,802,867,933,954,960,902,992,996,1176,1143,1196
%N Sum of divisors (sigma(n)) of the prime's previous and next numbers.
%H Charles R Greathouse IV, <a href="/A168567/b168567.txt">Table of n, a(n) for n = 1..10000</a>
%e a(1) = sigma(2-1) + sigma(2+1) = 1 + 4 = 5. a(3) = sigma(5-1) + sigma(5+1) = 7 + 12 = 19.
%t f[n_]:=Plus@@Divisors[n]; lst={};Do[p=Prime[n];AppendTo[lst,f[p-1]+f[p+1]],{n,5!}];lst
%t DivisorSigma[1,#-1]+DivisorSigma[1,#+1]&/@Prime[Range[60]] (* _Harvey P. Dale_, Jan 18 2019 *)
%o (PARI) apply(p->sigma(p-1)+sigma(p+1),primes(100)) \\ _Charles R Greathouse IV_, May 30 2013
%Y Cf. A000203.
%K nonn
%O 1,1
%A _Vladimir Joseph Stephan Orlovsky_, Nov 30 2009
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