A250245 -id:A250245 - cp's OEIS frontend

A302042 A032742 analog for a nonstandard factorization process based on the sieve of Eratosthenes (A083221).

1, 1, 1, 2, 1, 3, 1, 4, 3, 5, 1, 6, 1, 7, 5, 8, 1, 9, 1, 10, 9, 11, 1, 12, 5, 13, 7, 14, 1, 15, 1, 16, 15, 17, 7, 18, 1, 19, 11, 20, 1, 21, 1, 22, 21, 23, 1, 24, 7, 25, 25, 26, 1, 27, 25, 28, 27, 29, 1, 30, 1, 31, 13, 32, 11, 33, 1, 34, 33, 35, 1, 36, 1, 37, 17, 38, 11, 39, 1, 40, 39, 41, 1, 42, 35, 43, 35, 44, 1, 45, 49, 46, 45, 47, 13, 48

Offset: 1

Antti Karttunen, Mar 31 2018

nonn

Like [A020639(n), A032742(n)] also ordered pair [A020639(n), a(n)] is unique for each n. Iterating n, a(n), a(a(n)), a(a(a(n))), ..., until 1 is reached, and taking the smallest prime factor (A020639) of each term gives a multiset of primes in ascending order, unique for each natural number n >= 1. Permutation pair A250245/A250246 maps between this non-standard prime factorization of n and the ordinary prime factorization of n.

			For n = 66, A020639(66) [its smallest prime factor] is 2. Because A055396(66) = A000720(2) = 1, a(66) is just A078898(66) = 66/2 = 33.
For n = 33, A020639(33) = 3 and A055396(33) = 2, so a(33) = A250469(A078898(33)) = A250469(6) = 15. [15 is under 6 in array A083221].
For n = 15, A020639(15) = 3 and A055396(15) = 2, so a(15) = A250469(A078898(15)) = A250469(3) = 5. [5 is under 3 is array A083221].
For n = 5, A020639(5) = 5 and A055396(5) = 3, so a(5) = A250469(A250469(A078898(5))) = A250469(A250469(1)) = 1.
Collecting the primes given by A020639 we get a multiset of factors: [2, 3, 3, 5]. Note that 2*3*3*5 = 90 = A250246(66).
If we start from n = 66, iterating the map n -> A302044(n) [instead of n -> A302042(n)] and apply A020639 to each term obtained we get just a single instance of each prime: [2, 3, 5]. Then by applying A302045 to the same terms we get the corresponding exponents (multiplicities) of those primes: [1, 2, 1].

Antti Karttunen, Table of n, a(n) for n = 1..65537
Index entries for sequences generated by sieves

Cf. A020639, A032742, A055396, A078898, A083221, A250245, A250246, A250469, A268674, A276151, A280496, A302032.

Cf. also following analogs: A302041 (omega), A253557 (bigomega), A302043, A302044, A302045 (exponent of the least prime present), A302046 (prime signature filter), A302050 (Moebius mu), A302051 (tau), A302052 (char.fun of squares), A302039, A302055 (Arith. derivative).

\\ Assuming A250469 and its inverse A268674 have been precomputed, then the following is fast enough:
A302042(n) = if(1==n,n,my(k=0); while((n%2), n = A268674(n); k++); n = n/2; while(k>0, n = A250469(n); k--); (n));

A020639(n) = if(n>1, if(n>n=factor(n, 0)[1, 1], n, factor(n)[1, 1]), 1); \\ From A020639
A078898(n) = if(n<=1,n, my(spf=A020639(n),k=1,m=n/spf); while(m>1,if(A020639(m)>=spf,k++); m--); (k));
\\ Faster if we precompute A078898 as an ordinal transform of A020639:
up_to = 65537;
ordinal_transform(invec) = { my(om = Map(), outvec = vector(length(invec)), pt); for(i=1, length(invec), if(mapisdefined(om,invec[i]), pt = mapget(om, invec[i]), pt = 0); outvec[i] = (1+pt); mapput(om,invec[i],(1+pt))); outvec; };
v078898 = ordinal_transform(vector(up_to,n,A020639(n)));
A078898(n) = v078898[n];
A302042(n) = if((1==n)||isprime(n),1,my(c = A078898(n), p = prime(-1+primepi(A020639(n))+primepi(A020639(c))), d = A078898(c), k=0); while(d, k++; if((1==k)||(A020639(k)>=p),d -= 1)); (k*p));

For n > 1, a(n) = A250469^(r)(A078898(n)), where r = A055396(n)-1 and A250469^(r)(n) stands for applying r times the map x -> A250469(x), starting from x = n.
a(n) = A250245(A032742(A250246(n))) = A250245(A280496(n)) = A250245(A250246(n) / A020639(n)).
a(n) = n - A302043(n).

A302044 A028234 analog for factorization process based on the sieve of Eratosthenes (A083221).

Original entry on oeis.org

1, 1, 1, 1, 1, 3, 1, 1, 1, 5, 1, 3, 1, 7, 5, 1, 1, 9, 1, 5, 1, 11, 1, 3, 1, 13, 7, 7, 1, 15, 1, 1, 5, 17, 7, 9, 1, 19, 11, 5, 1, 21, 1, 11, 1, 23, 1, 3, 1, 25, 25, 13, 1, 27, 1, 7, 7, 29, 1, 15, 1, 31, 13, 1, 11, 33, 1, 17, 5, 35, 1, 9, 1, 37, 17, 19, 11, 39, 1, 5, 11, 41, 1, 21, 7, 43, 35, 11, 1, 45, 1, 23, 1, 47, 13, 3, 1, 49, 19, 25, 1, 51, 1, 13, 25

Offset: 1

Antti Karttunen, Mar 31 2018

nonn

Iterating n, a(n), a(a(n)), a(a(a(n))), ..., until 1 is reached, and taking the smallest prime factor (A020639) of each term gives a sequence of distinct primes in ascending order, while applying A302045 to the same terms gives the corresponding exponents (multiplicities) of those primes. Permutation pair A250245/A250246 maps between this non-standard prime factorization and the ordinary factorization of n. See also comments and examples in A302042.

Antti Karttunen, Table of n, a(n) for n = 1..65537
Index entries for sequences generated by sieves

Cf. A000265, A020639, A055396, A078898, A028234, A083221, A250245, A250246, A250469, A302034, A302042, A302045.

Cf. A302040 (positions of 1's).

\\ Assuming A250469 and its inverse A268674 have been precomputed, then the following is fast enough:
A302044(n) = if(1==n,n,my(k=0); while((n%2), n = A268674(n); k++); n = (n/2^valuation(n, 2)); while(k>0, n = A250469(n); k--); (n));

up_to = 65537;
ordinal_transform(invec) = { my(om = Map(), outvec = vector(length(invec)), pt); for(i=1, length(invec), if(mapisdefined(om,invec[i]), pt = mapget(om, invec[i]), pt = 0); outvec[i] = (1+pt); mapput(om,invec[i],(1+pt))); outvec; };
A000265(n) = (n/2^valuation(n, 2));
A020639(n) = if(n>1, if(n>n=factor(n, 0)[1, 1], n, factor(n)[1, 1]), 1); \\ From A020639
v078898 = ordinal_transform(vector(up_to,n,A020639(n)));
A078898(n) = v078898[n];
A302044(n) = { my(c = A000265(A078898(n))); if(1==c,1,my(p = prime(-1+primepi(A020639(n))+primepi(A020639(c))), d = A078898(c), k=0); while(d, k++; if((1==k)||(A020639(k)>=p),d -= 1)); (k*p)); };

For n > 1, a(n) = A250469^(r)(A000265(A078898(n))), where r = A055396(n)-1 and A250469^(r)(n) stands for applying r times the map x -> A250469(x), starting from x = n.

a(n) = A250245(A028234(A250246(n))).

A260741 Permutation of natural numbers: a(1) = 1, for n > 1: a(n) = A255127(A260438(n), a(A260439(n))).

Original entry on oeis.org

1, 2, 3, 4, 9, 6, 5, 8, 7, 18, 15, 12, 11, 10, 13, 16, 21, 14, 19, 36, 17, 30, 51, 24, 23, 22, 31, 20, 33, 26, 25, 32, 29, 42, 27, 28, 37, 38, 35, 72, 45, 34, 41, 60, 55, 102, 39, 48, 43, 46, 47, 44, 105, 62, 73, 40, 59, 66, 87, 52, 49, 50, 53, 64, 69, 58, 61, 84, 67, 54, 63, 56, 71, 74, 77, 76, 57, 70, 83, 144, 125, 90, 75, 68, 101, 82, 89, 120

Offset: 1

Antti Karttunen, Jul 30 2015

nonn

This is a more recursed variant of A260435.

Antti Karttunen, Table of n, a(n) for n = 1..10104
Index entries for sequences that are permutations of the natural numbers

Inverse: A260742.
Cf. A000959, A003309, A255127, A260438, A260439.
Similar permutations: A260435, A250245, A250246.

a(1) = 1, for n > 1: a(n) = A255127(A260438(n), a(A260439(n))).
Other identities. For all n >= 1:
a(A000959(n+1)) = A003309(n+2). [Maps Lucky numbers to odd Ludic numbers.]
a(n) = a(2n)/2. [The even bisection halved gives the sequence back.]

A260742 Permutation of natural numbers: a(1) = 1, for n > 1: a(n) = A255551(A260738(n), a(A260739(n))).

Original entry on oeis.org

1, 2, 3, 4, 7, 6, 9, 8, 5, 14, 13, 12, 15, 18, 11, 16, 21, 10, 19, 28, 17, 26, 25, 24, 31, 30, 35, 36, 33, 22, 27, 32, 29, 42, 39, 20, 37, 38, 47, 56, 43, 34, 49, 52, 41, 50, 51, 48, 61, 62, 23, 60, 63, 70, 45, 72, 77, 66, 57, 44, 67, 54, 71, 64, 123, 58, 69, 84, 65, 78, 73, 40, 55, 74, 83, 76, 75, 94, 103, 112, 101, 86, 79, 68, 91, 98, 59, 104, 87, 82, 93, 100, 89, 102

Offset: 1

Antti Karttunen, Jul 30 2015

nonn

This is a more recursed variant of A260436.

Antti Karttunen, Table of n, a(n) for n = 1..10104
Index entries for sequences that are permutations of the natural numbers

Inverse: A260741.
Cf. A000959, A003309, A255551, A260738, A260739.
Similar permutations: A260436, A250245, A250246.

a(1) = 1, for n > 1: a(n) = A255551(A260738(n), a(A260739(n))).
Other identities. For all n >= 1:
a(A003309(n+2)) = A000959(n+1). [Maps odd Ludic numbers to Lucky numbers.]
a(n) = a(2n)/2. [The even bisection halved gives the sequence back.]

A302045 a(1) = 0, for n > 1, a(n) = A001511(A078898(n)); Number of instances of the smallest prime factor A020639(n) in nonstandard factorization of n that is based on the sieve of Eratosthenes (A083221).

Original entry on oeis.org

0, 1, 1, 2, 1, 1, 1, 3, 2, 1, 1, 2, 1, 1, 1, 4, 1, 1, 1, 2, 3, 1, 1, 3, 2, 1, 1, 2, 1, 1, 1, 5, 2, 1, 1, 2, 1, 1, 1, 3, 1, 1, 1, 2, 4, 1, 1, 4, 2, 1, 1, 2, 1, 1, 3, 3, 2, 1, 1, 2, 1, 1, 1, 6, 1, 1, 1, 2, 3, 1, 1, 3, 1, 1, 1, 2, 1, 1, 1, 4, 2, 1, 1, 2, 2, 1, 1, 3, 1, 1, 3, 2, 5, 1, 1, 5, 1, 1, 1, 2, 1, 1, 1, 3, 2

Offset: 1

Antti Karttunen, Mar 31 2018

nonn

Iterating the map n -> A302044(n) until 1 is reached, and taking the smallest prime factor (A020639) of each term gives a sequence of distinct primes in ascending order, while applying this function (A302045) to those terms gives the corresponding "exponents" of those primes, that is, the count of consecutive occurrences of each prime when iterating the map n -> A302042(n), which gives the same primes with repetitions. Permutation pair A250245/A250246 maps between this non-standard prime factorization of n and the ordinary factorization of n. See also comments and examples in A302042.

Antti Karttunen, Table of n, a(n) for n = 1..65537
Index entries for sequences generated by sieves

Cf. A001511, A067029, A078898, A250245, A250246, A268674, A302042, A302044.

Cf. also A302035, A302050, A302051.

A020639(n) = { if(1==n,n,vecmin(factor(n)[, 1])); };
A078898(n) = { if(n<=1,n, my(spf=A020639(n),k=1,m=n/spf); while(m>1,if(A020639(m)>=spf,k++); m--); (k)); };
A001511(n) = 1+valuation(n,2);
A302045(n) = if(1==n,0,A001511(A078898(n)));

a(1) = 0, for n > 1, a(n) = A001511(A078898(n)).

For n > 1, a(n) = A250245(A067029(A250246(n))).

A250244 Permutation of natural numbers: a(n) = A249741(A055396(n+1), a(A246277(n+1))).

Original entry on oeis.org

1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 26, 21, 22, 23, 24, 25, 20, 27, 28, 29, 30, 31, 38, 33, 34, 35, 36, 37, 62, 51, 40, 41, 42, 43, 32, 45, 46, 47, 48, 49, 74, 39, 52, 53, 64, 55, 98, 57, 58, 59, 60, 61, 56, 75, 94, 65, 66, 67, 110, 69, 70, 71, 72, 73, 50, 123, 76, 101, 78, 79, 44, 81, 82, 83, 154, 85, 134, 63, 88, 89

Offset: 1

Antti Karttunen, Nov 16 2014

nonn

This is a "more recursed" variant of A249815. Preserves the parity of n.

Antti Karttunen, Table of n, a(n) for n = 1..8192
Index entries for sequences that are permutations of the natural numbers

Inverse: A250243.
Cf. A006093, A055396, A083221, A246277, A249741.
Similar or related permutations: A246683, A249814, A250245.
Differs from A249816 and A250243 for the first time at n=32, where a(32) = 38, while A249816(32) = A250243(32) = 44.
Differs from the "shallow variant" A249815 for the first time at n=39, where a(39) = 51, while A249815(39) = 39

a(n) = A249741(A055396(n+1), a(A246277(n+1))).
As a composition of other permutations:
a(n) = A249814(A246683(n)).
Other identities. For all n >= 1, the following holds:
a(n) = (1+a((2*n)-1)) / 2. [The odd bisection from a(1) onward with one added and then halved gives the sequence back.]
a(A006093(n)) = A006093(n). [Primes minus one are among the fixed points].

A302025 Permutation of natural numbers mapping ordinary factorization to "Ludic factorization": a(1) = 1, a(2n) = 2*a(n), a(A003961(n)) = A269379(a(n)).

Original entry on oeis.org

1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 23, 20, 27, 22, 25, 24, 19, 26, 21, 28, 29, 30, 37, 32, 39, 34, 35, 36, 41, 46, 63, 40, 43, 54, 47, 44, 33, 50, 53, 48, 31, 38, 75, 52, 61, 42, 65, 56, 99, 58, 67, 60, 71, 74, 57, 64, 95, 78, 77, 68, 135, 70, 83, 72, 89, 82, 51, 92, 59, 126, 91, 80, 45, 86, 97, 108, 155, 94, 147, 88

Offset: 1

Antti Karttunen, Apr 03 2018

nonn

See comments and examples in A302032 to see how Ludic factorization proceeds.

Cf. A302026 (inverse permutation).
Cf. A156552, A250245, A269171, A269387 (similar or related permutations).
Cf. A003961, A064989, A269379.

\\ With A269379 precomputed:
A064989(n) = {my(f); f = factor(n); if((n>1 && f[1,1]==2), f[1,2] = 0); for (i=1, #f~, f[i,1] = precprime(f[i,1]-1)); factorback(f)};
A302025(n) = if(1==n,n,if(!(n%2),2*A302025(n/2),A269379(A302025(A064989(n)))));
(Scheme, with memoization-macro definec)
(definec (A302025 n) (cond ((= 1 n) n) ((even? n) (* 2 (A302025 (/ n 2)))) (else (A269379 (A302025 (A064989 n))))))

a(1) = 1, a(2n) = 2*a(n), a(2n+1) = A269379(a(A064989(2n+1))).
a(n) = A269171(A250245(n)).
a(n) = A269387(A156552(n)).

A302040 Numbers k such that A078898(k) is a power of 2; an analog for A000961 based on factorization-kind of process involving the sieve of Eratosthenes (A083221).

Original entry on oeis.org

1, 2, 3, 4, 5, 7, 8, 9, 11, 13, 16, 17, 19, 21, 23, 25, 29, 31, 32, 37, 41, 43, 45, 47, 49, 53, 55, 59, 61, 64, 67, 71, 73, 79, 83, 89, 91, 93, 97, 101, 103, 107, 109, 113, 115, 121, 127, 128, 131, 137, 139, 149, 151, 157, 163, 167, 169, 173, 179, 181, 187, 189, 191, 193, 197, 199, 203, 211, 223, 227, 229, 233, 235, 239, 241, 247, 251, 256, 257

Offset: 1

Antti Karttunen, Apr 02 2018

nonn

Numbers k for which A302041(k) < 2, or equally, for which A302044(k) = 1.
Sequence A250245(A000961(k)) sorted into ascending order, or in other words, numbers k such that A250246(k) is a prime power (in A000961).
Numbers k such that all terms in iteration sequence k, A302042(k), A302042(A302042(k)), A302042(A302042(A302042(k))), ..., have an equal smallest prime factor (A020639) before the sequence settles to 1, in other words, that they all stay on the same row of A083221. This also forces the column position of each (A078898) to be a power of 2 (A000079).

			For k = 21 = 3*7, the smallest prime factor is 3. A302042(21) = 9, and A302042(9) = 3, both (9 and 3) which also have 3 as their smallest prime factor, and after that the sequence settles to 1, as A302042(3) = 1, thus 21 is included in this sequence.
For k = 27 = 3*3*3, the smallest prime factor is 3. However, A302042(27) = 7, thus 27 is not included in this sequence.

Antti Karttunen, Table of n, a(n) for n = 1..6883
Index entries for sequences generated by sieves

Cf. A000961, A078898, A302036, A302041, A302044, A302053.

Cf. A000040, A000079, A001248 (subsequences).

for(n=1,257,if(2>A302041(n),print1(n,","))); \\ Other code as in A302041.

A302053 Squares (A000290) analog for nonstandard factorization process based on the sieve of Eratosthenes (A083221).

Original entry on oeis.org

0, 1, 4, 9, 16, 25, 36, 45, 49, 64, 100, 105, 115, 121, 144, 169, 180, 189, 196, 203, 256, 265, 289, 297, 341, 361, 400, 420, 429, 460, 469, 475, 481, 484, 529, 537, 576, 585, 676, 697, 720, 745, 756, 765, 784, 803, 812, 817, 833, 841, 961, 1024, 1027, 1060, 1075, 1081, 1156, 1188, 1197, 1257, 1309, 1345, 1364, 1369, 1377, 1411, 1444

Offset: 0

Antti Karttunen, Mar 31 2018

nonn

Indexing starts with zero, with a(0) = 0, to match with the indexing of A000290.
After initial zero, gives the positions of odd terms in A302051.
After initial zero, contains values obtained with A250245(n^2) sorted into ascending order, or in other words, numbers n such that A250246(n) is a square (in A000290).
Numbers n such that for all terms in iteration sequence n, A302044(n), A302044(A302044(n)), A302044(A302044(A302044(n))), ..., applying A302045(n) gives an even number before the sequence settles to 1.

Antti Karttunen, Table of n, a(n) for n = 0..3283
Index entries for sequences generated by sieves

Cf. A000290, A250245, A302051, A302040, A302044, A302045, A302052 (characteristic function).

Cf. A000302, A001248 (subsequences).

for(n=0,4096,if(1==A302052(n),print1(n,",")));

A279348 a(1) = 1, for n > 1, if A079559(n) = 0, a(n) = 2*a(A256992(n)), otherwise a(n) = A250469(a(A256992(n))).

Original entry on oeis.org

1, 2, 3, 5, 4, 6, 7, 9, 10, 15, 11, 8, 12, 14, 25, 27, 18, 35, 13, 20, 30, 21, 33, 22, 39, 49, 16, 24, 28, 50, 65, 51, 54, 77, 17, 36, 70, 57, 87, 26, 55, 85, 40, 60, 42, 63, 95, 66, 121, 45, 44, 78, 69, 81, 98, 147, 119, 32, 48, 56, 100, 130, 125, 159, 102, 143, 19, 108, 154, 105, 207, 34, 145, 215, 72, 140, 114, 75, 91, 174, 133, 117, 52

Offset: 1

Antti Karttunen, Dec 12 2016

nonn

Antti Karttunen, Table of n, a(n) for n = 1..8192
Index entries for sequences that are permutations of the natural numbers

Inverse: A279349.
Cf. A005187, A055938, A079559, A250469, A256992.
Related or similar permutations: A250245, A252753, A252755, A279338, A279341, A279343.

(definec (A279348 n) (cond ((= 1 n) n) ((zero? (A079559 n)) (* 2 (A279348 (A256992 n)))) (else (A250469 (A279348 (A256992 n))))))

a(1) = 1, for n > 1, if A079559(n) = 0 [when n is a term of A055938], a(n) = 2*a(A256992(n)), otherwise a(n) = A250469(a(A256992(n))).
As a composition of other permutations:
a(n) = A250245(A279338(n)).
a(n) = A252753(A279343(n)).
a(n) = A252755(A279341(n)).

cp's OEIS Frontend

A302042 A032742 analog for a nonstandard factorization process based on the sieve of Eratosthenes (A083221).

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A302044 A028234 analog for factorization process based on the sieve of Eratosthenes (A083221).

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A260741 Permutation of natural numbers: a(1) = 1, for n > 1: a(n) = A255127(A260438(n), a(A260439(n))).

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A260742 Permutation of natural numbers: a(1) = 1, for n > 1: a(n) = A255551(A260738(n), a(A260739(n))).

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A302045 a(1) = 0, for n > 1, a(n) = A001511(A078898(n)); Number of instances of the smallest prime factor A020639(n) in nonstandard factorization of n that is based on the sieve of Eratosthenes (A083221).

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A250244 Permutation of natural numbers: a(n) = A249741(A055396(n+1), a(A246277(n+1))).

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A302025 Permutation of natural numbers mapping ordinary factorization to "Ludic factorization": a(1) = 1, a(2n) = 2*a(n), a(A003961(n)) = A269379(a(n)).

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A302040 Numbers k such that A078898(k) is a power of 2; an analog for A000961 based on factorization-kind of process involving the sieve of Eratosthenes (A083221).

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A302053 Squares (A000290) analog for nonstandard factorization process based on the sieve of Eratosthenes (A083221).

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