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 A072454 Count of all nontotients in the reduced residue system of 2n-1. 1
 0, 0, 1, 2, 2, 4, 5, 4, 8, 9, 5, 11, 10, 10, 15, 16, 11, 13, 20, 14, 23, 24, 15, 26, 23, 19, 30, 23, 21, 33, 34, 22, 27, 38, 28, 41, 42, 26, 37, 47, 35, 49, 37, 37, 53, 44, 38, 43, 59, 41, 62, 63, 32, 65, 66, 46, 68, 55, 46, 58, 69, 53, 64, 79, 55, 81, 65, 50, 85, 86, 60, 77, 72 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,4 LINKS FORMULA a(n)=A072451(n)-1+A072453(n) EXAMPLE n=105: Phi[105]=48 with 24 odd, 24 even terms in reduced residue system, of which 9 even terms and (all but 1) odd term is nontotient: a([105+1]/2)=a(53)=24-1+9=32. n=21: reduced residue system[21]=Union[{1,5,11,13,17,19},{2,4,8,16,20}] includes 6 odd and 5 even numbers. No even nontotients terms in reduced residue system[21], so 6-1=5 odd terms give all nontotients, so a([21+1]/2)=a(11)=5. CROSSREFS Cf. A000010, A037225, A072451-A072455, A005277, A002202. Sequence in context: A210597 A252836 A286101 * A115216 A208637 A252938 Adjacent sequences:  A072451 A072452 A072453 * A072455 A072456 A072457 KEYWORD nonn AUTHOR Labos Elemer, Jun 19 2002 STATUS approved

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Last modified June 12 10:58 EDT 2021. Contains 344947 sequences. (Running on oeis4.)