A355926 Square array A(n,k) = A355442(A246278(n,k)), read by falling antidiagonals.

3, 9, 1, 5, 5, 1, 3, 5, 1, 1, 3, 125, 7, 1, 1, 5, 5, 343, 1, 1, 1, 3, 175, 7, 11, 1, 1, 1, 9, 1, 49, 1, 1, 1, 1, 1, 25, 125, 7, 121, 1, 1, 1, 1, 1, 3, 245, 2401, 1, 1, 1, 1, 1, 1, 1, 3, 1, 77, 1, 1, 1, 1, 1, 1, 1, 1, 5, 5, 49, 11, 28561, 1, 1, 1, 1, 1, 1, 1, 3, 175, 7, 121, 1, 1, 1, 1, 1, 1, 1, 1, 1, 9, 5, 77, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1

Offset: 1

Author

Antti Karttunen, Jul 22 2022

Keywords

• nonn
• tabl

Examples

			The top left corner of the array:
   n= 1  2  3    4  5    6  7      8    9   10 11     12 13   14  15       16
  2n= 2  4  6    8 10   12 14     16   18   20 22     24 26   28  30       32
----+--------------------------------------------------------------------------
  1 | 3, 9, 5,   3, 3,   5, 3,     9,  25,   3, 3,     5, 3,   9,  7,       3,
  2 | 1, 5, 5, 125, 5, 175, 1,   125, 245,   1, 5,   175, 5,   5, 35,       1,
  3 | 1, 1, 7, 343, 7,  49, 7,  2401,  77,  49, 7,    77, 7,  49, 77,   16807,
  4 | 1, 1, 1,  11, 1, 121, 1,     1,  11, 121, 1, 17303, 1, 121, 11,    1331,
  5 | 1, 1, 1,   1, 1,   1, 1, 28561,   1,   1, 1,  2197, 1,   1, 13,   28561,
  6 | 1, 1, 1,   1, 1,   1, 1,     1,   1,   1, 1,    17, 1,   1,  1, 1419857,
  7 | 1, 1, 1,   1, 1,   1, 1,     1,   1,   1, 1,     1, 1,   1,  1,     361,
  8 | 1, 1, 1,   1, 1,   1, 1,     1,   1,   1, 1,     1, 1,   1,  1,       1,
  9 | 1, 1, 1,   1, 1,   1, 1,     1,   1,   1, 1,     1, 1,   1,  1,       1,
		

Crossrefs

Cf. A003961, A246278, A276086, A355442, A355835.

Cf. also A355924, A355925 for similarly constructed arrays.

Programs

PARI

up_to = 105;
A003961(n) = { my(f = factor(n)); for(i=1, #f~, f[i, 1] = nextprime(f[i, 1]+1)); factorback(f); };
A276086(n) = { my(m=1, p=2); while(n, m *= (p^(n%p)); n = n\p; p = nextprime(1+p)); (m); };
A355442(n) = gcd(A003961(n), A276086(n));
A246278sq(row,col) = if(1==row,2*col, my(f = factor(2*col)); for(i=1, #f~, f[i,1] = prime(primepi(f[i,1])+(row-1))); factorback(f));
A355926sq(row,col) = A355442(A246278sq(row,col));
A355926list(up_to) = { my(v = vector(up_to), i=0); for(a=1,oo, for(col=1,a, i++; if(i > up_to, return(v)); v[i] = A355926sq(col,(a-(col-1))))); (v); };
v355926 = A355926list(up_to);
A355926(n) = v355926[n];