cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

A340441 Square array, read by ascending antidiagonals, where row n gives all odd solutions k > 1 and n > 0 to A000120(2*n+1) = A000120((2*n+1)*k), A000120 is the Hamming weight.

Original entry on oeis.org

3, 13, 11, 3, 205, 43, 57, 5, 3277, 171, 35, 3641, 7, 52429, 683, 21, 47, 233017, 19, 838861, 2731, 3, 79, 99, 14913081, 23, 13421773, 10923, 241, 5, 197, 187, 954437177, 37, 214748365, 43691, 7, 61681, 7, 325, 419, 61083979321, 39, 3435973837, 174763
Offset: 1

Views

Author

Thomas Scheuerle, Jan 07 2021

Keywords

Comments

Solutions to related equation A000120(k) = A000120(k*n) are A340351.

Examples

			Five initial terms of rows 1-5 are listed below:
   1:  3,   11,     43,       171,       683, ...
   2: 13,  205,   3277,     52429,    838861, ...
   3:  3,    5,      7,        19,        23, ...
   4: 57, 3641, 233017,  14913081, 954437177, ...
   5: 35,   47,      99,      187,       419, ...
T(3,4) = 19 because: (3*2+1) in binary is 111 and (3*2+1)*19 = 133 in binary is 10000101, both have 3 bits set to 1.
		

Crossrefs

Cf. A263132 (superset of 1st row), A007583 (1st row), A299960 (2nd row).

Formula

If 2*n = 2^j, then T(n, m) = (1+2^(j+2*j*m))/(2*n+1) for m > 0. In particular:
T(1, m) = (1+2^(1+2*m))/3 = A007583(m),
T(2, m) = (1+2^(2+4*m))/5 = A299960(m),
T(4, m) = (1+2^(3+6*m))/9.
The third row consists of all numbers of the form (1+2^(1+b*3)+2^(2+c*3))/7, where b and c are natural numbers >= 0 and b+c > 0.
The seventh row consists of all numbers of the form (1+2^(1+b*2)+2^(2+c*2)+2^(3+d*2))/15 where b, c, and d are natural numbers >= 0 and b+c+d > 1.

Extensions

More terms from Pontus von Brömssen, Jan 08 2021