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 A194886 Units' digits of the nonzero decagonal numbers. 0
 1, 0, 7, 2, 5, 6, 5, 2, 7, 0, 1, 0, 7, 2, 5, 6, 5, 2, 7, 0, 1, 0, 7, 2, 5, 6, 5, 2, 7, 0, 1, 0, 7, 2, 5, 6, 5, 2, 7, 0, 1, 0, 7, 2, 5, 6, 5, 2, 7, 0, 1, 0, 7, 2, 5, 6, 5, 2, 7, 0, 1, 0, 7, 2, 5, 6, 5, 2, 7, 0, 1, 0, 7, 2, 5, 6, 5, 2, 7, 0, 1, 0, 7, 2, 5, 6 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 COMMENTS This is a periodic sequence with period 10 and cycle 1,0,7,2,5,6,5,2,7,0. LINKS FORMULA a(n) = a(n-10). a(n) = 35 -a(n-1) -a(n-2) -a(n-3) -a(n-4) -a(n-5) -a(n-6) -a(n-7) -a(n-8) -a(n-9). a(n) = mod(n(4n-3),10). G.f.: x*(1 +7*x^2 +2*x^3 +5*x^4 +6*x^5 +5*x^6 +2*x^7 +7*x^8)/((1-x)*(1+x)*(1 +x +x^2 +x^3 +x^4)*(1 -x +x^2 -x^3 +x^4)). a(n) = -n^2 + 2*n (mod 10). - Arkadiusz Wesolowski, Jul 03 2012 a(n) = A010879(A001107(n)). - Michel Marcus, Aug 10 2015 EXAMPLE The seventh nonzero decagonal number is A001107(7)=175, which has units' digit 5. Hence a(7)=5. MATHEMATICA Table[Mod[n (4 n - 3), 10], {n, 86}] PadRight[{}, 120, {1, 0, 7, 2, 5, 6, 5, 2, 7, 0}] (* Harvey P. Dale, Aug 17 2019 *) CROSSREFS Cf. A001107, A010879. Sequence in context: A199080 A093072 A066903 * A196764 A074457 A200237 Adjacent sequences:  A194883 A194884 A194885 * A194887 A194888 A194889 KEYWORD nonn,easy,base AUTHOR Ant King, Sep 07 2011 STATUS approved

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Last modified April 9 04:05 EDT 2020. Contains 333343 sequences. (Running on oeis4.)