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A168567
Sum of divisors (sigma(n)) of the prime's previous and next numbers.
1
5, 10, 19, 27, 46, 52, 70, 81, 96, 128, 135, 151, 186, 180, 196, 218, 258, 264, 270, 339, 309, 354, 350, 414, 423, 433, 426, 442, 496, 488, 567, 588, 558, 624, 638, 672, 632, 657, 732, 668, 816, 882, 868, 802, 867, 933, 954, 960, 902, 992, 996, 1176, 1143, 1196
OFFSET
1,1
LINKS
Charles R Greathouse IV, Table of n, a(n) for n = 1..10000
EXAMPLE
a(1) = sigma(2-1) + sigma(2+1) = 1 + 4 = 5. a(3) = sigma(5-1) + sigma(5+1) = 7 + 12 = 19.
MATHEMATICA
f[n_]:=Plus@@Divisors[n]; lst={}; Do[p=Prime[n]; AppendTo[lst, f[p-1]+f[p+1]], {n, 5!}]; lst
DivisorSigma[1, #-1]+DivisorSigma[1, #+1]&/@Prime[Range[60]] (* Harvey P. Dale, Jan 18 2019 *)
PROG
(PARI) apply(p->sigma(p-1)+sigma(p+1), primes(100)) \\ Charles R Greathouse IV, May 30 2013
CROSSREFS
Cf. A000203.
Sequence in context: A030776 A115289 A358306 * A185440 A134467 A178132
KEYWORD
nonn
AUTHOR
STATUS
approved