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 A130686 Absolute difference of final digits of two consecutive triangular numbers. 1
 1, 2, 3, 6, 5, 4, 7, 2, 1, 0, 1, 2, 7, 4, 5, 6, 3, 2, 1, 0, 1, 2, 3, 6, 5, 4, 7, 2, 1, 0, 1, 2, 7, 4, 5, 6, 3, 2, 1, 0, 1, 2, 3, 6, 5, 4, 7, 2, 1, 0, 1, 2, 7, 4, 5, 6, 3, 2, 1, 0, 1, 2, 3, 6, 5, 4, 7, 2, 1, 0, 1, 2, 7, 4, 5, 6, 3, 2, 1, 0, 1, 2, 3, 6, 5, 4, 7, 2, 1, 0, 1, 2, 7, 4, 5, 6, 3, 2, 1, 0, 1, 2, 3, 6, 5 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Periodic with period 20. LINKS Index entries for linear recurrences with constant coefficients, signature (0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1). FORMULA a(n)=abs{ A010879[A000217(n+1)] - A010879[A000217(n)] }. - R. J. Mathar, Jul 15 2007 a(n)=(1/950)*{-32*(n mod 20)+63*[(n+1) mod 20]+63*[(n+2) mod 20]+63*[(n+3) mod 20]+158*[(n+4) mod 20]-32*[(n+5) mod 20]-32*[(n+6) mod 20]+158*[(n+7) mod 20]-222*[(n+8) mod 20]-32*[(n+9) mod 20]-32*[(n+10) mod 20]+63*[(n+11) mod 20]+63*[(n+12) mod 20]+253*[(n+13) mod 20]-127*[(n+14) mod 20]+63*[(n+15) mod 20]+63*[(n+16) mod 20]-127*[(n+17) mod 20]-32*[(n+18) mod 20]-32*[(n+19) mod 20]}, with n>=0. - Paolo P. Lava, Oct 23 2008 MAPLE A000217 := proc(n) n*(n+1)/2 ; end: A010879 := proc(n) n mod 10 ; end: A130686 := proc(n) abs(A010879(A000217(n+1))-A010879(A000217(n))) ; end: seq(A130686(n), n=0..80) ; # R. J. Mathar, Jul 15 2007 CROSSREFS Cf. A008954. Sequence in context: A299207 A277330 A072298 * A213927 A222241 A056023 Adjacent sequences:  A130683 A130684 A130685 * A130687 A130688 A130689 KEYWORD base,easy,nonn AUTHOR Giovanni Teofilatto, Jun 30 2007 STATUS approved

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Last modified March 18 22:11 EDT 2019. Contains 321305 sequences. (Running on oeis4.)