A378089 - OEIS

%I #8 Nov 18 2024 22:30:39

%S 1,3,8,10,18,24,30,5,9,15,28,40,72,84,90,120,7,21,26,56,70,78,108,126,

%T 168,210,34,45,52,102,140,156,252,360,420,11,33,88,110,198,264,330,13,

%U 35,39,63,76,104,105,130,228,234,280,312,390,504,540,630,840,58,98,174,294

%N Irregular triangle read by rows in which row n lists the numbers k such that phi(k)/tau(k) = n.

%e Triangle begins:

%e   n=1: 1, 3, 8, 10, 18, 24, 30;

%e   n=2: 5, 9, 15, 28, 40, 72, 84, 90, 120;

%e   n=3: 7, 21, 26, 56, 70, 78, 108, 126, 168, 210;

%e   n=4: 34, 45, 52, 102, 140, 156, 252, 360, 420;

%e   n=5: 11, 33, 88, 110, 198, 264, 330;

%e   n=6: 13, 35, 39, 63, 76, 104, 105, 130, 228, 234, 280, 312, 390, 504, 540, 630, 840;

%e   n=7: 58, 98, 174, 294;

%e   ...

%Y Cf. A000005 (tau), A000010 (phi).

%Y Cf. A020488 (row 1), A062516 (row 2), A063469 (row 3), A063470 (row 4).

%Y Cf. A112954 (row lengths), A175667 (1st column), A112955 (right column), A020491 (ordered terms).

%K nonn,tabf

%O 1,2

%A _Mohammed Yaseen_, Nov 16 2024