A377094 Inverse permutation to A377093.

1, 2, 4, 3, 7, 5, 12, 19, 6, 8, 27, 38, 50, 13, 9, 20, 63, 80, 98, 10, 14, 28, 117, 21, 11, 51, 140, 15, 167, 196, 226, 22, 29, 64, 16, 39, 257, 99, 52, 23, 294, 17, 335, 30, 378, 118, 423, 24, 18, 470, 65, 53, 520, 81, 31, 25, 100, 168, 573, 40, 632, 227, 693

Offset: 1

Author

Rémy Sigrist, Oct 16 2024

Keywords

• nonn

Examples

			A377093(42) = 84, so a(84) = 42.
		

Links

• Rémy Sigrist, Table of n, a(n) for n = 1..10000
• Rémy Sigrist, C++ program
• Index entries for sequences that are permutations of the natural numbers

Crossrefs

Cf. A377093.

Programs

Python

from itertools import count, islice
def agen(): # generator of terms; uses A377093gen() in A377093
    adict, n = dict(), 1
    for k, v in enumerate(A377093gen(), 1):
        if v not in adict:
            adict[v] = k
            while n in adict: yield adict[n]; n += 1
print(list(islice(agen(), 63))) # Michael S. Branicky, Oct 16 2024

Formula

a(n) <= (n-1)*n/2 + 1. - Michael S. Branicky, Oct 16 2024