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 A061728 Start with (a, b) = (2, 4). The next pair (a', b') is ((b + 1) mod 10, (a + 1) mod 10) where (a, b) is the previous pair. 2
 2, 4, 5, 3, 4, 6, 7, 5, 6, 8, 9, 7, 8, 0, 1, 9, 0, 2, 3, 1, 2, 4, 5, 3, 4, 6, 7, 5, 6, 8, 9, 7, 8, 0, 1, 9, 0, 2, 3, 1, 2, 4, 5, 3, 4, 6, 7, 5, 6, 8, 9, 7, 8, 0, 1, 9, 0, 2, 3, 1, 2, 4, 5, 3, 4, 6, 7, 5, 6, 8, 9, 7, 8, 0, 1, 9, 0, 2, 3, 1, 2, 4, 5, 3, 4, 6, 7, 5, 6, 8, 9, 7, 8, 0, 1, 9, 0, 2, 3, 1, 2, 4, 5, 3, 4 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Has period 20. REFERENCES Norman Sullivan, Test Your Own IQ, Workman Publishing Co. New York, NY, 1994, pp. 49, 51. LINKS Harry J. Smith, Table of n, a(n) for n = 1..1000 Index entries for linear recurrences with constant coefficients, signature (1,-1,1,-1,1,-1,1,-1,1,-1,1,-1,1,-1,1,-1,1,-1,1). FORMULA From Colin Barker, Jul 02 2018: (Start) G.f.: x*(2 + 2*x + 3*x^2 + 4*x^4 + 2*x^5 + 5*x^6 + 6*x^8 + 2*x^9 + 7*x^10 + 8*x^12 - 8*x^13 + 9*x^14 + 2*x^17 + x^18) / ((1 - x)*(1 + x^2)*(1 - x + x^2 - x^3 + x^4)*(1 + x + x^2 + x^3 + x^4)*(1 - x^2 + x^4 - x^6 + x^8)). a(n) = 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-10) + a(n-11) - a(n-12) + a(n-13) - a(n-14) + a(n-15) - a(n-16) + a(n-17) - a(n-18) + a(n-19) for n>19. (End) a(1) = 2, a(2) = 4. {a(n+1), a(n+2)} = (1 + {a(n), a(n - 1)}) mod 10. - Michael De Vlieger, Jul 01 2018 a(n) = (2*floor(n/4) + floor(3*(n mod 4)/2) + 1) mod 10. - Jon E. Schoenfield, Jul 01 2018 EXAMPLE 24 (42)-> 53, (35)-> 46, (64)-> 75. MATHEMATICA Nest[Append[#, Mod[1 + {#2, #1}, 10] & @@ #[[-1]]] &, {{2, 4}}, 42] // Flatten (* Michael De Vlieger, Jul 01 2018 *) PROG (PARI) { f="b061728.txt"; for (n=1, 500, if (n==1, a=2; b=4, s=a; a=(b + 1)%10; b=(s + 1)%10); write(f, 2*n - 1, " ", a); write(f, 2*n, " ", b) ) } \\ Harry J. Smith, Jul 27 2009 (PARI) Vec(x*(2 + 2*x + 3*x^2 + 4*x^4 + 2*x^5 + 5*x^6 + 6*x^8 + 2*x^9 + 7*x^10 + 8*x^12 - 8*x^13 + 9*x^14 + 2*x^17 + x^18) / ((1 - x)*(1 + x^2)*(1 - x + x^2 - x^3 + x^4)*(1 + x + x^2 + x^3 + x^4)*(1 - x^2 + x^4 - x^6 + x^8)) + O(x^150)) \\ Colin Barker, Jul 02 2018 CROSSREFS Cf. A061729. Sequence in context: A071286 A021807 A284561 * A332017 A276127 A182115 Adjacent sequences: A061725 A061726 A061727 * A061729 A061730 A061731 KEYWORD nonn,easy,base AUTHOR Jason Earls, May 06 2001 EXTENSIONS More terms from Larry Reeves (larryr(AT)acm.org), May 07 2001 Offset changed from 24 to 1 by Harry J. Smith, Jul 27 2009 Name edited by David A. Corneth and Jon E. Schoenfield, Jul 05 2018 Edited by N. J. A. Sloane, Jul 06 2018 STATUS approved

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Last modified April 16 08:27 EDT 2024. Contains 371698 sequences. (Running on oeis4.)