A296421 a(1) = 1, a(2) = 2, a(3) = 3, a(4) = a(5) = 4, a(6) = a(7) = 6; a(n) = a(n-a(n-1)) + a(n-a(n-2)) + a(n-a(n-3)) for n > 7.

1, 2, 3, 4, 4, 6, 6, 8, 7, 9, 9, 10, 11, 11, 12, 12, 14, 16, 13, 16, 16, 19, 16, 20, 17, 22, 19, 22, 21, 24, 22, 26, 22, 28, 24, 29, 26, 28, 29, 30, 30, 31, 32, 32, 33, 33, 34, 35, 35, 36, 36, 38, 40, 39, 38, 42, 41, 42, 44, 41, 43, 45, 51, 40, 44, 53, 46, 51, 44, 55, 47, 53, 54, 51, 55

Offset: 1

Author

Altug Alkan, Dec 12 2017

Keywords

• nonn
• look

Links

• Altug Alkan, Table of n, a(n) for n = 1..10000
• Altug Alkan, Alternative scatterplot of A296421
• Altug Alkan, Scatterplot of a(n) - 2*n/3

Crossrefs

Cf. A005185, A284644, A278055, A292351.

Programs

Mathematica

Fold[Append[#1, #1[[#2 - #1[[#2 - 1]] ]] + #1[[#2 - #1[[#2 - 2]] ]] + #1[[#2 - #1[[#2 - 3]] ]] ] &, {1, 2, 3, 4, 4, 6, 6}, Range[8, 75]] (* Michael De Vlieger, Dec 12 2017 *)

PARI

q=vector(10^5); q[1]=1;q[2]=2;q[3]=3;q[4]=4;q[5]=4;q[6]=6;q[7]=6;for(n=8, #q, q[n] = q[n-q[n-1]]+q[n-q[n-2]]+q[n-q[n-3]]); q