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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 September 24 19:27 EDT 2021. Contains 347651 sequences. (Running on oeis4.)