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 A308095 a(n) is the sum of sigma (i.e., A000203) over the totatives of n. 1
 1, 1, 4, 5, 15, 7, 33, 19, 40, 26, 87, 27, 127, 50, 84, 82, 220, 59, 277, 90, 187, 140, 407, 103, 401, 193, 352, 207, 660, 127, 762, 309, 485, 339, 646, 244, 1098, 423, 677, 390, 1342, 268, 1480, 525, 758, 639, 1758, 416, 1666, 581, 1191, 770, 2250, 527, 1742, 821, 1527, 1016, 2786, 502, 3014 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 COMMENTS a(n) <= A024916(n-1) for n >= 2, with equality if and only if n is prime. LINKS Robert Israel, Table of n, a(n) for n = 1..10000 Robert Israel, Plot of a(n)/n^2 for 1 <= n <= 20000 FORMULA a(n) = Sum_{1<=k<=n; gcd(k,n)=1} A000203(k). EXAMPLE a(3) = sigma(1) + sigma(2) = 4. MAPLE f:= proc(n) local k; add(numtheory:-sigma(k), k=select(t -> igcd(t, n)=1, [\$1..n])) end proc; map(f, [\$1..100]); PROG (PARI) a(n) = sum(k=1, n, if (gcd(n, k)==1, sigma(k))); \\ Michel Marcus, May 13 2019 CROSSREFS Cf. A000203, A024916, A307997. Sequence in context: A222501 A225204 A363817 * A321348 A257311 A369790 Adjacent sequences: A308092 A308093 A308094 * A308096 A308097 A308098 KEYWORD nonn,look AUTHOR J. M. Bergot and Robert Israel, May 12 2019 STATUS approved

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Last modified August 2 21:25 EDT 2024. Contains 374875 sequences. (Running on oeis4.)