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 A320109 Filter sequence for counting the residue classes mod 8 of divisors of n. 5
 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 3, 11, 5, 12, 13, 14, 15, 16, 3, 17, 13, 6, 7, 18, 19, 10, 20, 21, 5, 22, 7, 23, 20, 24, 13, 25, 5, 6, 13, 26, 15, 22, 3, 11, 27, 12, 7, 28, 29, 30, 20, 17, 5, 31, 13, 32, 20, 10, 3, 33, 5, 12, 34, 35, 36, 31, 3, 37, 13, 22, 7, 38, 15, 10, 39, 11, 13, 22, 7, 40, 41, 24, 3, 33, 36, 6, 13, 18, 15, 42, 13, 21, 13, 12, 13, 43, 15, 44, 45, 46, 5, 31, 7, 26 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Restricted growth sequence transform of A320108. For all i, j: a(i) = a(j) => A320115(i) = A320115(j). LINKS Antti Karttunen, Table of n, a(n) for n = 1..100000 PROG (PARI) up_to = 100000; A320108(n) = { my(m=1); fordiv(n, d, if(d>1, m *= prime(1+(d%8)))); (m); }; rgs_transform(invec) = { my(om = Map(), outvec = vector(length(invec)), u=1); for(i=1, length(invec), if(mapisdefined(om, invec[i]), my(pp = mapget(om, invec[i])); outvec[i] = outvec[pp] , mapput(om, invec[i], i); outvec[i] = u; u++ )); outvec; }; v320109 = rgs_transform(vector(up_to, n, A320108(n))); A320109(n) = v320109[n]; CROSSREFS Cf. A320108, A320113, A320115, A320117. Sequence in context: A351868 A325721 A079050 * A278062 A254597 A064698 Adjacent sequences: A320106 A320107 A320108 * A320110 A320111 A320112 KEYWORD nonn AUTHOR Antti Karttunen, Oct 06 2018 STATUS approved

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Last modified June 15 08:58 EDT 2024. Contains 373402 sequences. (Running on oeis4.)