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A026474 a(n) = least positive integer > a(n-1) and not equal to a(i)+a(j) or a(i)+a(j)+a(k) for 1<=i<j<k<n (a 3-Stohr sequence). 13
1, 2, 4, 8, 15, 22, 29, 36, 43, 50, 57, 64, 71, 78, 85, 92, 99, 106, 113, 120, 127, 134, 141, 148, 155, 162, 169, 176, 183, 190, 197, 204, 211, 218, 225, 232, 239, 246, 253, 260, 267, 274, 281, 288, 295, 302, 309, 316, 323, 330, 337, 344, 351, 358, 365, 372 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
COMMENTS
All h-Stohr sequences have formula: h terms 1,2,..,2^(n-1),..,2^(h-1) and then continue (2^h-1)(n-h)+1. - Henry Bottomley, Feb 04 2000
LINKS
Eric Weisstein's World of Mathematics, Stoehr Sequence.
FORMULA
Starts 1, 2, 4 then the numbers 7*(n-3)+1.
a(n) = 7*n-20 for n>3. a(n) = 2*a(n-1)-a(n-2) for n>5. G.f.: x*(1+x^2+2*x^3+3*x^4)/(1-x)^2. - Colin Barker, Sep 19 2012
MATHEMATICA
Join[{1, 2, 4, 8}, Range[15, 500, 7]] (* Vladimir Joseph Stephan Orlovsky, Jan 27 2012 *)
CoefficientList[Series[(1 + x^2 + 2 x^3 + 3 x^4)/(1 - x)^2, {x, 0, 60}], x] (* Vincenzo Librandi, Oct 18 2013 *)
LinearRecurrence[{2, -1}, {1, 2, 4, 8, 15}, 60] (* Harvey P. Dale, May 14 2018 *)
PROG
(Magma) [1, 2, 4] cat [7*n+1: n in [1..60]]; // Vincenzo Librandi, Oct 18 2013
(PARI) a(n)=if(n>3, 7*n-20, 2^(n-1)) \\ Charles R Greathouse IV, Sep 17 2015
CROSSREFS
Sequence in context: A288313 A213020 A279858 * A301629 A339507 A305992
KEYWORD
nonn,easy
AUTHOR
EXTENSIONS
More terms from Eric W. Weisstein
STATUS
approved

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Last modified March 28 13:42 EDT 2024. Contains 371254 sequences. (Running on oeis4.)