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 A280987 {Concatenation n, n-1, n-2, ...3,2,1} mod sigma(n). 1
 0, 0, 1, 2, 3, 9, 1, 6, 4, 1, 9, 21, 1, 9, 9, 16, 9, 24, 1, 33, 17, 1, 9, 21, 0, 9, 1, 41, 21, 33, 17, 6, 33, 19, 33, 25, 25, 21, 1, 1, 33, 81, 17, 21, 45, 1, 33, 85, 49, 69, 57, 77, 27, 81, 1, 81, 1, 1, 21, 57, 59, 81, 33, 60, 21, 33, 45, 51, 81, 1, 9, 66, 41, 9, 97, 1, 81, 81, 1, 57, 117, 73, 33, 145 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,4 LINKS Indranil Ghosh, Table of n, a(n) for n = 1..10000 FORMULA a(n) = A000422(n) mod A000203(n). EXAMPLE For n = 11, A000422(n) mod sigma(n) = 1110987654321 mod 12 = 9. S0 a(11) = 9. MATHEMATICA Table[Mod[FromDigits[Flatten[IntegerDigits/@Range[n, 1, -1]]], DivisorSigma[ 1, n]], {n, 90}] (* Harvey P. Dale, Jul 01 2020 *) PROG (Python) def sigma(n): s=0 for i in range(1, n+1): if n%i==0: s+=i return s def C(n): s="" for i in range(n, 0, -1): s+=str(i) return int(s) for i in range(1, 10001): print str(i)+" "+str(C(i)%sigma(i)) CROSSREFS Cf. A000203, A000422, A114795. Sequence in context: A201407 A109197 A021811 * A030367 A028508 A021422 Adjacent sequences: A280984 A280985 A280986 * A280988 A280989 A280990 KEYWORD nonn,base AUTHOR Indranil Ghosh, Jan 12 2017 STATUS approved

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Last modified August 3 08:07 EDT 2024. Contains 374885 sequences. (Running on oeis4.)