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 A184593 5n - A101306: sum_{i=1..n} the last digit of prime(i). 2
 3, 5, 5, 3, 7, 9, 7, 3, 5, 1, 5, 3, 7, 9, 7, 9, 5, 9, 7, 11, 13, 9, 11, 7, 5, 9, 11, 9, 5, 7, 5, 9, 7, 3, -1, 3, 1, 3, 1, 3, -1, 3, 7, 9, 7, 3, 7, 9, 7, 3, 5, 1, 5, 9, 7, 9, 5, 9, 7, 11, 13, 15, 13, 17, 19, 17, 21, 19, 17, 13, 15, 11, 9, 11, 7, 9, 5, 3, 7, 3 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS The differences are always odd since the parity of A101306 and n are always opposite. Positions where a(n)=2k-1 for k>0; 10, 1, 2, 5, 6, 20, 21, 62, 64, 65, 67, 198, 761, 765, 764, 800, ... - Robert G. Wilson v, Jun 06 2012 LINKS Table of n, a(n) for n=1..80. FORMULA a(n) = 5*n - Sum_{i=1..n} Prime(i) (mod 10). MATHEMATICA f[n_] := 5n - Sum[ Mod[ Prime@ k, 10], {k, n}]; Array[f, 80] Rest@ FoldList[# + 5 - Mod[Prime@ #2, 10] &, 0, Range@ 80] CROSSREFS Cf. A101306, A122754, A184594. Sequence in context: A053670 A085963 A282177 * A328154 A249304 A333906 Adjacent sequences: A184590 A184591 A184592 * A184594 A184595 A184596 KEYWORD base,easy,sign AUTHOR Robert G. Wilson v, Jan 17 2011 STATUS approved

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Last modified June 24 19:44 EDT 2024. Contains 373690 sequences. (Running on oeis4.)