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 A061008 a(n) = Sum_{j=1..n} (-(n-1)! mod n). 4
 0, 1, 2, 4, 5, 5, 6, 6, 6, 6, 7, 7, 8, 8, 8, 8, 9, 9, 10, 10, 10, 10, 11, 11, 11, 11, 11, 11, 12, 12, 13, 13, 13, 13, 13, 13, 14, 14, 14, 14, 15, 15, 16, 16, 16, 16, 17, 17, 17, 17, 17, 17, 18, 18, 18, 18, 18, 18, 19, 19, 20, 20, 20, 20, 20, 20, 21, 21, 21, 21, 22, 22, 23, 23, 23 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 LINKS Vincenzo Librandi, Table of n, a(n) for n = 1..5000 FORMULA a(n) = a(n-1) + A061007(n) = A061009(n) + 2. For n > 3, a(n) = pi(n) + 2 where pi(n) = A000720(n) is the number of primes less than or equal to n. EXAMPLE a(6) = 5 since (-1 mod 1) + (-1 mod 2) + (-2 mod 3) + (-6 mod 4) + (-24 mod 5) + (-120 mod 6) = 0 + 1 + 1 + 2 + 1 + 0 = 5. MAPLE P:=proc(n) local a, i, k, w; a:=0; print(a); for i from 1 by 1 to n do w:=((i-1)! mod (i+1)); a:=a+w; print(a); od; end: P(1000); # Paolo P. Lava, Apr 23 2007 MATHEMATICA Join[{0, 1, 2}, a[n_]:= 2 + PrimePi[n]; Table[a[n], {n, 4, 100}]] (* Vincenzo Librandi, Aug 11 2017 *) PROG (MAGMA) [0, 1, 2] cat [ 2+#PrimesUpTo(n): n in [4..200] ]; // Vincenzo Librandi, Aug 11 2017 CROSSREFS Cf. A000040, A000142, A061006, A061007, A061009. Sequence in context: A227401 A131813 A083038 * A256720 A091988 A023824 Adjacent sequences:  A061005 A061006 A061007 * A061009 A061010 A061011 KEYWORD nonn AUTHOR Henry Bottomley, Apr 12 2001 STATUS approved

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Last modified May 11 16:26 EDT 2021. Contains 343798 sequences. (Running on oeis4.)