A171887 Records in A171868 (positions).

1, 2, 4, 9, 20, 50, 147, 269, 992, 1000, 4297, 76468, 97314, 445519, 1315337, 2594742, 3888902, 91859035, 92411466, 1180624310, 4501485474, 11288114818, 23434425843

Offset

1,2

Links

Table of n, a(n) for n=1..23.

Rémy Sigrist, C program for A171887

Prog

(Python)
A181391_list, A171887_list, l, r, k = [0, 0], [1], 0, 1, 1
for n in range(1, 10**6):
    for m in range(n-1, -1, -1):
        if A181391_list[m] == A181391_list[n]:
            A181391_list.append(n-m)
            break
    else:
        A181391_list.append(0)
        k += 1
        if n-l > r:
            r = n-l
            A171887_list.append(k)
        l = n # Chai Wah Wu, Jan 02 2015
(C) // See Links section.

Crossrefs

Cf. A181391, A171865, A171868, A171888.

Sequence in context: A006648 A128496 A134955 * A027881 A002861 A363203

Adjacent sequences: A171884 A171885 A171886 * A171888 A171889 A171890

Keyword

nonn,more

Author

N. J. A. Sloane, Oct 18 2010

Extensions

a(12)-a(13) from Chai Wah Wu, Jan 02 2015

a(14)-a(17) from Rémy Sigrist, Jun 11 2019

a(18)-a(23) from Benjamin Chaffin, Sep 11 2019

Status

approved