A049891 a(n) = a(1) + a(2) + ... + a(n-1) - a(m) for n >= 4, where m = 2*n - 2 - 2^(p+1) and p is the unique integer such that 2^p < n - 1 <= 2^(p+1), starting with a(1) = a(2) = 1 and a(3) = 2.

1, 1, 2, 3, 4, 10, 18, 29, 39, 106, 210, 413, 807, 1537, 2767, 4410, 5947, 16303, 32604, 65201, 130383, 260689, 521071, 1041018, 2079163, 4146433, 8243968, 16292448, 31804567, 60503719, 108861423, 173511575, 234015294, 641542162

Offset: 1

Author

Clark Kimberling

Keywords

• nonn

Crossrefs

Cf. A049890 (similar, but with minus a(m/2)), A049938 (similar, but with plus a(m/2)), A049939 (similar, but with plus a(m)).

Programs

PARI

lista(nn) = { nn = max(nn, 3); my(va = vector(nn)); va[1] = 1; va[2] = 1; va[3] = 2; my(sa = vecsum(va)); for (n=4, nn, va[n] = sa - va[2*(n - 1 - 2^logint(n-2, 2))]; sa += va[n]; ); va; } \\ Petros Hadjicostas, May 03 2020

Extensions

Name edited by Petros Hadjicostas, May 03 2020