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 A075693 Difference between 10-adic numbers defined in A018248 & A018247. 2
 1, 5, -3, 9, -9, -7, 5, 7, 5, -7, 7, -9, -9, -1, 5, -3, -1, 5, 5, -9, 3, -5, -5, -9, -9, 7, -3, -3, 9, 7, 1, 9, 9, -9, 9, 7, -3, -9, -7, 9, 3, 5, 3, 5, 1, 3, 5, 1, -5, -1, -1, 9, 9, 9, 7, 7, -7, 3, -3, -7, 9, -7, -1, -9, 9, -1, -3, -3, 7, 5, -3, 9, 9, -9, -7, -9, 9, -1, -7, 3, -9, 5, 9, -7 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Numbers in A018247 and A018248 are known as automorphic numbers in base 10, meaning that the infinite integers a=(...256259918212890625) or b=(...743740081787109376) provides a nontrivial solution to x*x == x (mod any power of 10). Read backwards so as to match their counterparts (A007185 & A016090), A018247(1)+A018248(1) = 11 & A018247(n)+A018248(n) = 9 for all n's > 1 and their product is A076308. All entries must be odd. Is the accumulative sum equally positive and negative, i.e. does the sum equal 0 infinitely often? LINKS MATHEMATICA (* execute the programming in both A018247 & A018248 *) Reverse[b - a] aa[n_] := For[t = 5; k = 1, True, k++, t = Mod[t^2, 10^k]; If[k == n, Return[ Quotient[t, 10^(n-1)]]]]; bb[n_] := Reap[ For[t = 6; k = 1, k <= n , k++, t = Mod[t^5, 10^k]; Sow[ Quotient[10*t, 10^k]]]][[2, 1, n]]; a[n_] := bb[n] - aa[n]; Table[a[n], {n, 1, 84}](* Jean-François Alcover, May 25 2012, after Paul D. Hanna *) CROSSREFS Cf. A018248 & A018247. Sequence in context: A201938 A201410 A019955 * A198134 A082454 A108245 Adjacent sequences:  A075690 A075691 A075692 * A075694 A075695 A075696 KEYWORD easy,sign,base AUTHOR Robert G. Wilson v, Sep 26 2002 STATUS approved

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