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 A107816 a(n) = sigma(A067651(n)). 2
 1, 8, 20, 48, 144, 240, 720, 480, 756, 720, 864, 2304, 2880, 4080, 5040, 6240, 6048, 6720, 9984, 21600, 90720, 506880, 806400, 748800, 973440, 1153152 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Numbers n such that n = sigma(k) = phi(prime(k)-1) for some k. Values of k are in A067651, values of prime(k) are in A107815. LINKS EXAMPLE a(3) = sigma(A067651(3)) = sigma(19) = 20. PROG (PARI) m=400000; for(n=1, m, s=sigma(n); if(s==eulerphi(prime(n)-1), print1(s, ", "))) CROSSREFS Cf. A067651, A107815. Sequence in context: A273266 A273304 A169878 * A205219 A232401 A036835 Adjacent sequences:  A107813 A107814 A107815 * A107817 A107818 A107819 KEYWORD nonn,more AUTHOR Klaus Brockhaus, May 24 2005 STATUS approved

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Last modified September 25 03:11 EDT 2021. Contains 347651 sequences. (Running on oeis4.)