A360371 -id:A360371 - cp's OEIS frontend

A361251 Inverse permutation to A360371.

1, 2, 3, 4, 6, 5, 7, 10, 8, 9, 11, 12, 15, 16, 13, 14, 21, 17, 22, 18, 23, 28, 29, 19, 24, 20, 30, 36, 37, 31, 45, 25, 38, 27, 39, 46, 55, 56, 26, 32, 66, 47, 67, 35, 48, 78, 79, 40, 91, 58, 34, 33, 92, 57, 69, 44, 68, 105, 106, 80, 120, 54, 93, 49, 41, 43

Offset: 1

Rémy Sigrist, Mar 30 2023

nonn

			A360371(42) = 68, so a(68) = 42.

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

Cf. A360371.

PARI
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A361748 Triangle T(n, k) of distinct positive integers, n > 0, k = 1..n, read by rows and filled in the greedy way such that T(n, k) is a multiple of T(n, 1).

Original entry on oeis.org

1, 2, 4, 3, 6, 9, 5, 10, 15, 20, 7, 14, 21, 28, 35, 8, 16, 24, 32, 40, 48, 11, 22, 33, 44, 55, 66, 77, 12, 36, 60, 72, 84, 96, 108, 120, 13, 26, 39, 52, 65, 78, 91, 104, 117, 17, 34, 51, 68, 85, 102, 119, 136, 153, 170, 18, 54, 90, 126, 144, 162, 180, 198, 216, 234, 252

Offset: 1

Rémy Sigrist, Mar 30 2023

This sequence is a variant of A360371.

As a flat sequence, this is a permutation of the positive integers with inverse A361939.

			Triangle T(n, k) begins:
     1;
     2,  4;
     3,  6,  9;
     5, 10, 15, 20;
     7, 14, 21, 28, 35;
     8, 16, 24, 32, 40,  48;
    11, 22, 33, 44, 55,  66,  77;
    12, 36, 60, 72, 84,  96, 108, 120;
    13, 26, 39, 52, 65,  78,  91, 104, 117;
    17, 34, 51, 68, 85, 102, 119, 136, 153, 170;
    ...

Michael De Vlieger, Table of n, a(n) for n = 1..11325 (rows n = 1..150)
Rémy Sigrist, PARI program
Index entries for sequences that are permutations of the natural numbers

Cf. A360371, A361939 (inverse).

nn = 11; c[] = False; T[1, 1] = 1; c[1] = True; u = 2; Do[If[j == 1, k = u; m = 1, While[c[k m], m++]]; Set[{T[i, j], c[#]}, {#, True}] &[k m]; If[k == u, While[c[u], u++]], {i, 2, nn}, {j, i}]; Table[T[i, j], {i, nn}, {j, i}] // Flatten (* _Michael De Vlieger, Apr 01 2023 *)

PARI
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See Links section.
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T(n, k) = k * T(n, 1) when T(n, 1) is a prime number.

cp's OEIS Frontend

A361251 Inverse permutation to A360371.

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