OFFSET
1,2
COMMENTS
Considered as a binary operation on the positive integers, A(x, y) returns the term of the Doudna-sequence from the position that is the sum of the positions of x and y in the same sequence. (This is based on giving the Doudna-sequence an offset of 0, rather than 1 as used in A005940.) - Peter Munn, Feb 14 2021
LINKS
FORMULA
EXAMPLE
The top left 16x16 corner of the array:
1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16,
2, 3, 4, 5, 6, 9, 10, 7, 8, 15, 14, 25, 22, 21, 12, 11,
3, 4, 5, 6, 9, 8, 15, 10, 7, 12, 21, 18, 33, 20, 25, 14,
4, 5, 6, 9, 8, 7, 12, 15, 10, 25, 20, 27, 28, 35, 18, 21,
5, 6, 9, 8, 7, 10, 25, 12, 15, 18, 35, 16, 55, 30, 27, 20,
6, 9, 8, 7, 10, 15, 18, 25, 12, 27, 30, 11, 42, 45, 16, 35,
7, 10, 15, 12, 25, 18, 11, 16, 27, 14, 49, 20, 77, 50, 21, 24,
8, 7, 10, 15, 12, 25, 16, 27, 18, 11, 24, 21, 40, 49, 14, 45,
9, 8, 7, 10, 15, 12, 27, 18, 25, 16, 45, 14, 63, 24, 11, 30,
10, 15, 12, 25, 18, 27, 14, 11, 16, 21, 50, 35, 70, 75, 20, 49,
11, 14, 21, 20, 35, 30, 49, 24, 45, 50, 13, 36, 121, 22, 75, 32,
12, 25, 18, 27, 16, 11, 20, 21, 14, 35, 36, 45, 60, 125, 30, 75,
13, 22, 33, 28, 55, 42, 77, 40, 63, 70, 121, 60, 17, 98, 105, 48,
14, 21, 20, 35, 30, 45, 50, 49, 24, 75, 22, 125, 98, 33, 36, 13,
15, 12, 25, 18, 27, 16, 21, 14, 11, 20, 75, 30, 105, 36, 35, 50,
16, 11, 14, 21, 20, 35, 24, 45, 30, 49, 32, 75, 48, 13, 50, 81,
PROG
(PARI)
up_to = 105;
A005940(n) = { my(p=2, t=1); n--; until(!n\=2, if((n%2), (t*=p), p=nextprime(p+1))); (t); };
A156552(n) = { my(f = factor(n), p2 = 1, res = 0); for(i = 1, #f~, p = 1 << (primepi(f[i, 1]) - 1); res += (p * p2 * (2^(f[i, 2]) - 1)); p2 <<= f[i, 2]); res };
A341510list(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] = A341510sq(col, (a-(col-1))))); (v); };
v341510 = A341510list(up_to);
A341510(n) = v341510[n];
CROSSREFS
KEYWORD
nonn,tabl
AUTHOR
Antti Karttunen, Feb 13 2021
STATUS
approved