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A376358
Positions of numbers in A007961 that end in 1.
4
1, 5, 10, 14, 17, 21, 26, 30, 35, 37, 41, 46, 50, 54, 59, 63, 65, 69, 74, 78, 82, 86, 91, 95, 98, 101, 105, 110, 114, 117, 122, 126, 131, 135, 138, 142, 145, 149, 154, 158, 161, 165, 170, 174, 179, 183, 186, 190, 195, 197, 201, 206, 210, 213, 217, 222, 226
OFFSET
1,2
COMMENTS
Every positive integer is in exactly one of these sequences: A376358, this sequence, A376359, or A376360.
Conjecture: {a(n+1) - a(n) : n >= 1} = {2,3,4,5,6,7}. (See related conjectures at A376357, A376359, and A376360.)
MATHEMATICA
a[n_, poly_] := FromDigits[FoldList[{Mod[#[[1]], #2], Quotient[#[[1]], #2]} &, {n, 0}, Reverse[Map[(poly - 2) # (# - 1)/2 + # &,
Range[Floor[Sqrt[2 n]]]]]][[All, 2]]]
t4 = Map[a[#, 4] &, Range[200]]; (* A007961 *)
m = Mod[t4, 10];
Table[Flatten[Position[m, r]], {r, 0, 2}]
p0 = Flatten[Position[m, 0]] (* A376357 *)
p1 = Flatten[Position[m, 1]] (* this sequence *)
p2 = Flatten[Position[m, 2]] (* A376359 *)
p3 = Flatten[Position[m, 3]] (* A376360 *)
(* Peter J. C. Moses, Sep 20 2024 *)
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Clark Kimberling, Sep 25 2024
STATUS
approved