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

Author

N. J. A. Sloane, Oct 18 2010

Keywords

• nonn
• more

Links

• Rémy Sigrist, C program for A171887

Crossrefs

Cf. A181391, A171865, A171868, A171888.

Programs

C

// See Links section.

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

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