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A104244
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Suppose m = Product_{i=1..k} p_i^e_i, where p_i is the i-th prime number and each e_i is a nonnegative integer. Then we can define P_m(x) = Sum_{i=1..k} e_i*x^(i-1). The sequence is the square array A(n,m) = P_m(n) read by descending antidiagonals.
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14
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0, 1, 0, 1, 1, 0, 2, 2, 1, 0, 1, 2, 3, 1, 0, 2, 4, 2, 4, 1, 0, 1, 3, 9, 2, 5, 1, 0, 3, 8, 4, 16, 2, 6, 1, 0, 2, 3, 27, 5, 25, 2, 7, 1, 0, 2, 4, 3, 64, 6, 36, 2, 8, 1, 0, 1, 5, 6, 3, 125, 7, 49, 2, 9, 1, 0, 3, 16, 10, 8, 3, 216, 8, 64, 2, 10, 1, 0, 1, 4, 81, 17, 10, 3, 343, 9, 81, 2, 11, 1, 0, 2, 32, 5
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OFFSET
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1,7
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COMMENTS
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The square array A(row,col) is read by downwards antidiagonals as: A(1,1), A(1,2), A(2,1), A(1,3), A(2,2), A(3,1), etc.
A(n,m) (entry at row=n, column=m) gives the evaluation at x=n of the polynomial (with nonnegative integer coefficients) bijectively encoded in the prime factorization of m. See A206284, A206296 for the details of that encoding. (The roles of variables n and m were accidentally swapped in this description, corrected by Antti Karttunen, Oct 30 2016)
(End)
Each row is a completely additive sequence, row n mapping prime(m) to n^(m-1). - Peter Munn, Apr 22 2022
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LINKS
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FORMULA
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A(n,A206296(k)) = A073133(n,k). [This formula demonstrates how this array can be used with appropriately encoded polynomials. Note that A073133 reads its antidiagonals by ascending order, while here the order is opposite.] - Antti Karttunen, Oct 30 2016
The sequence is defined by the following identities:
A(n, 3) = n;
A(n, m*k) = A(n, m) + A(n, k);
A(n, A297845(m, k)) = A(n, m) * A(n, k).
(End)
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EXAMPLE
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a(13) = 3 because 3 = p_1^0 * p_2^1 * p_3^0 * ..., so P_3(x) = 0*x^(1-1) + 1*x^(2-1) + 0*x^(3-1) + ... = x. Hence a(13) = A(3,3) = P_3(3) = 3. [Elaborated by Peter Munn, Aug 13 2022]
The top left corner of the array:
0, 1, 1, 2, 1, 2, 1, 3, 2, 2, 1, 3, 1, 2, 2, 4
0, 1, 2, 2, 4, 3, 8, 3, 4, 5, 16, 4, 32, 9, 6, 4
0, 1, 3, 2, 9, 4, 27, 3, 6, 10, 81, 5, 243, 28, 12, 4
0, 1, 4, 2, 16, 5, 64, 3, 8, 17, 256, 6, 1024, 65, 20, 4
0, 1, 5, 2, 25, 6, 125, 3, 10, 26, 625, 7, 3125, 126, 30, 4
0, 1, 6, 2, 36, 7, 216, 3, 12, 37, 1296, 8, 7776, 217, 42, 4
0, 1, 7, 2, 49, 8, 343, 3, 14, 50, 2401, 9, 16807, 344, 56, 4
0, 1, 8, 2, 64, 9, 512, 3, 16, 65, 4096, 10, 32768, 513, 72, 4
0, 1, 9, 2, 81, 10, 729, 3, 18, 82, 6561, 11, 59049, 730, 90, 4
0, 1, 10, 2, 100, 11, 1000, 3, 20, 101, 10000, 12, 100000, 1001, 110, 4
...
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PROG
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(MIT/GNU Scheme, with Aubrey Jaffer's SLIB Scheme library)
(require 'factor)
(define (A104244bi row col) (fold-left (lambda (sum p.e) (+ sum (* (cdr p.e) (expt row (- (A000720 (car p.e)) 1))))) 0 (if (= 1 col) (list) (elemcountpairs (sort (factor col) <)))))
(define (elemcountpairs lista) (let loop ((pairs (list)) (lista lista) (prev #f)) (cond ((not (pair? lista)) (reverse! pairs)) ((equal? (car lista) prev) (set-cdr! (car pairs) (+ 1 (cdar pairs))) (loop pairs (cdr lista) prev)) (else (loop (cons (cons (car lista) 1) pairs) (cdr lista) (car lista))))))
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CROSSREFS
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For completely additive sequences with primes p mapped to a function of p, see A001414.
For completely additive sequences where some primes are mapped to 1, the rest to 0 (notably, some ruler functions) see the cross-references in A249344.
For completely additive sequences, s, with primes p mapped to a function of s(p-1) and maybe s(p+1), see A352957.
See the comments for the relevance of A206284.
A297845 represents multiplication of the relevant polynomials.
A167219 lists columns that contain their own column number.
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KEYWORD
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AUTHOR
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EXTENSIONS
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Name edited (and aligned with rest of sequence) by Peter Munn, Apr 23 2022
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STATUS
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approved
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