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A130686
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Absolute difference of final digits of two consecutive triangular numbers.
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1
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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; internal format)
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OFFSET
| 1,2
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COMMENTS
| Periodic with period 20.
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FORMULA
| a(n)=abs{ A010879[A000217(n+1)] - A010879[A000217(n)] }. - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), 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 [From Paolo P. Lava (paoloplava(AT)gmail.com), Oct 23 2008]
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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 (mathar(AT)strw.leidenuniv.nl), Jul 15 2007
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CROSSREFS
| Cf. A008954.
Sequence in context: A011159 A091556 A072298 * A056023 A133259 A120067
Adjacent sequences: A130683 A130684 A130685 * A130687 A130688 A130689
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KEYWORD
| base,easy,nonn
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AUTHOR
| Giovanni Teofilatto (g.teofilatto(AT)tiscalinet.it), Jun 30 2007
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