OFFSET
1,2
COMMENTS
If k is a term, then k*(k+1)*(k+2)*...*(k+6)/(k+(k+1)+(k+2)+...+(k+6)) is a multiple of k.
LINKS
Index entries for linear recurrences with constant coefficients, signature (1,0,0,0,1,-1).
FORMULA
Equals natural numbers minus '4, 7, 11, 14, 18, ...' (= previous term +3, +4, +3, +4, ...).
G.f.: x*(x^5 + x^4 + 2*x^3 + x^2 + x + 1)/((1-x)*(1-x^5)).
a(n) = (m^3 - 6*m^2 + 17*m + 6*(7*floor(n/5)-1))/6, where m = n mod 5. - Luce ETIENNE,Oct 17 2018
MATHEMATICA
#+{1, 2, 3, 5, 6}&/@(7*Range[0, 15])//Flatten (* or *) LinearRecurrence[ {1, 0, 0, 0, 1, -1}, {1, 2, 3, 5, 6, 8}, 100] (* Harvey P. Dale, Oct 07 2018 *)
PROG
(Magma) [n: n in [0..120] | n mod 7 in {1, 2, 3, 5, 6}]; // Vincenzo Librandi, Dec 29 2010
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Patrick De Geest, May 15 1998
STATUS
approved