cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

Showing 1-9 of 9 results.

A332818 a(n) = A108548(A003961(A332808(n))).

Original entry on oeis.org

1, 3, 5, 9, 7, 15, 13, 27, 25, 21, 17, 45, 11, 39, 35, 81, 19, 75, 29, 63, 65, 51, 37, 135, 49, 33, 125, 117, 23, 105, 41, 243, 85, 57, 91, 225, 31, 87, 55, 189, 43, 195, 53, 153, 175, 111, 61, 405, 169, 147, 95, 99, 47, 375, 119, 351, 145, 69, 73, 315, 59, 123, 325, 729, 77, 255, 89, 171, 185, 273, 97, 675, 67, 93, 245, 261, 221, 165, 101
Offset: 1

Views

Author

Antti Karttunen, Feb 27 2020

Keywords

Comments

Permutation of odd numbers. Preserves prime signature.

Crossrefs

Cf. A332819 (a left inverse).

Programs

Formula

Fully multiplicative with a(2) = 3, a(A002145(n)) = A002144(n) and a(A002144(n)) = A002145(1+n), for all n >= 1.
a(n) = A108548(A003961(A332808(n))).
A332819(a(n)) = n.
A046523(a(n)) = A046523(n).

A332819 a(n) = A108548(A064989(A332808(n))).

Original entry on oeis.org

1, 1, 2, 1, 3, 2, 5, 1, 4, 3, 13, 2, 7, 5, 6, 1, 11, 4, 17, 3, 10, 13, 29, 2, 9, 7, 8, 5, 19, 6, 37, 1, 26, 11, 15, 4, 23, 17, 14, 3, 31, 10, 41, 13, 12, 29, 53, 2, 25, 9, 22, 7, 43, 8, 39, 5, 34, 19, 61, 6, 47, 37, 20, 1, 21, 26, 73, 11, 58, 15, 89, 4, 59, 23, 18, 17, 65, 14, 97, 3, 16, 31, 101, 10, 33, 41, 38, 13, 67, 12, 35, 29
Offset: 1

Views

Author

Antti Karttunen, Feb 27 2020

Keywords

Crossrefs

A left inverse of A332818.

Programs

Formula

Fully multiplicative with a(2) = 1, a(3) = 2, a(A002144(n)) = A002145(n), and a(A002145(1+n)) = A002144(n) for all n >= 1.
a(n) = A108548(A064989(A332808(n))).
a(A332818(n)) = n.

A332816 a(n) = A156552(A332808(n)).

Original entry on oeis.org

0, 1, 2, 3, 4, 5, 8, 7, 6, 9, 32, 11, 16, 17, 10, 15, 64, 13, 128, 19, 18, 65, 512, 23, 12, 33, 14, 35, 256, 21, 2048, 31, 66, 129, 20, 27, 1024, 257, 34, 39, 4096, 37, 8192, 131, 22, 1025, 32768, 47, 24, 25, 130, 67, 16384, 29, 68, 71, 258, 513, 131072, 43, 65536, 4097, 38, 63, 36, 133, 524288, 259, 1026, 41, 2097152, 55, 262144, 2049, 26, 515
Offset: 1

Views

Author

Antti Karttunen, Feb 28 2020

Keywords

Crossrefs

Cf. A332815 (inverse permutation).

Programs

  • PARI
    up_to = 26927;
    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}; \\ From A156552
    A332806list(up_to) = { my(v=vector(2), xs=Map(), lista=List([]), p,q,u); v[2] = 3; v[1] = 5; mapput(xs,1,1); mapput(xs,2,2); mapput(xs,3,3);  for(n=4,up_to, p = v[2-(n%2)]; q = nextprime(1+p); while(q%4 != p%4, q=nextprime(1+q)); v[2-(n%2)] = q; mapput(xs,primepi(q),n)); for(i=1, oo, if(!mapisdefined(xs, i, &u), return(Vec(lista)), listput(lista, prime(u)))); };
    v332806 = A332806list(up_to);
    A332806(n) = v332806[n];
    A332808(n) = { my(f=factor(n)); f[,1] = apply(A332806,apply(primepi,f[,1])); factorback(f); };
    A332816(n) = A156552(A332808(n));

Formula

a(n) = A156552(A332808(n)).
For n > 1, A070939(a(n)) = A332894(n).
For n >= 1: (Start)
A080791(a(n)) = A332899(n)-1.
Among many identities given in A156552 that apply here as well we have for example the following ones:
A000120(a(n)) = A001222(n).
A069010(a(n)) = A001221(n).
A106737(a(n)) = A000005(n).
(End)

A332811 a(n) = A243071(A332808(n)).

Original entry on oeis.org

0, 1, 3, 2, 7, 6, 15, 4, 5, 14, 63, 12, 31, 30, 13, 8, 127, 10, 255, 28, 29, 126, 1023, 24, 11, 62, 9, 60, 511, 26, 4095, 16, 125, 254, 27, 20, 2047, 510, 61, 56, 8191, 58, 16383, 252, 25, 2046, 65535, 48, 23, 22, 253, 124, 32767, 18, 123, 120, 509, 1022, 262143, 52, 131071, 8190, 57, 32, 59, 250, 1048575, 508, 2045, 54, 4194303, 40, 524287, 4094, 21
Offset: 1

Views

Author

Antti Karttunen, Mar 05 2020

Keywords

Crossrefs

Cf. A332817 (inverse permutation).
Cf. also A332215.

Programs

  • PARI
    up_to = 26927;
    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)};
    A243071(n) = if(n<=2, n-1, if(!(n%2), 2*A243071(n/2), 1+(2*A243071(A064989(n)))));
    A332806list(up_to) = { my(v=vector(2), xs=Map(), lista=List([]), p,q,u); v[2] = 3; v[1] = 5; mapput(xs,1,1); mapput(xs,2,2); mapput(xs,3,3);  for(n=4,up_to, p = v[2-(n%2)]; q = nextprime(1+p); while(q%4 != p%4, q=nextprime(1+q)); v[2-(n%2)] = q; mapput(xs,primepi(q),n)); for(i=1, oo, if(!mapisdefined(xs, i, &u), return(Vec(lista)), listput(lista, prime(u)))); };
    v332806 = A332806list(up_to);
    A332806(n) = v332806[n];
    A332808(n) = { my(f=factor(n)); f[,1] = apply(A332806,apply(primepi,f[,1])); factorback(f); };
    A332811(n) = A243071(A332808(n));

Formula

a(n) = A243071(A332808(n)).
For n > 1, a(n) = A054429(A332816(n)).
a(n) = A332895(n) + A332896(n).
a(n) = A332895(n) OR A332896(n) = A332895(n) XOR A332896(n).
A000120(a(n)) = A332899(n).

A108548 Fully multiplicative with a(prime(j)) = A108546(j), where A108546 is the lexicographically earliest permutation of primes such that after 2 the forms 4*k+1 and 4*k+3 alternate, and prime(j) is the j-th prime in A000040.

Original entry on oeis.org

1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 13, 12, 11, 14, 15, 16, 17, 18, 19, 20, 21, 26, 29, 24, 25, 22, 27, 28, 23, 30, 37, 32, 39, 34, 35, 36, 31, 38, 33, 40, 41, 42, 43, 52, 45, 58, 53, 48, 49, 50, 51, 44, 47, 54, 65, 56, 57, 46, 61, 60, 59, 74, 63, 64, 55, 78, 73, 68, 87, 70, 67, 72
Offset: 1

Views

Author

Reinhard Zumkeller, Jun 10 2005

Keywords

Comments

Multiplicative with a(2^e) = 2^e, else if p is the m-th prime then a(p^e) = q^e where q is the m/2-th prime of the form 4*k + 3 (A002145) for even m and a(p^e) = r^e where r is the (m-1)/2-th prime of the form 4*k + 1 (A002144) for odd m. - David A. Corneth, Apr 25 2022
Permutation of the natural numbers with fixed points A108549: a(A108549(n)) = A108549(n).

Crossrefs

Cf. A002144, A002145, A049084, A108546, A108549 (fixed points), A332808 (inverse permutation).
Cf. also A332815, A332817 (this permutation applied to Doudna tree and its mirror image), also A332818, A332819.
Cf. also A267099, A332212 and A348746 for other similar mappings.

Programs

  • Mathematica
    terms = 72;
    A111745 = Module[{prs = Prime[Range[2 terms]], m3, m1, min},
         m3 = Select[prs, Mod[#, 4] == 3&];
         m1 = Select[prs, Mod[#, 4] == 1&];
         min = Min[Length[m1], Length[m3]];
         Riffle[Take[m3, min], Take[m1, min]]];
    A108546[n_] := If[n == 1, 2, A111745[[n - 1]]];
    A049084[n_] := PrimePi[n]*Boole[PrimeQ[n]];
    a[n_] := If[n == 1, 1, Module[{p, e}, Product[{p, e} = pe; A108546[A049084[p]]^e, {pe, FactorInteger[n]}]]];
    Array[a, terms] (* Jean-François Alcover, Nov 19 2021, using Harvey P. Dale's code for A111745 *)
  • PARI
    up_to = 26927; \\ One of the prime fixed points.
    A108546list(up_to) = { my(v=vector(up_to), p,q); v[1] = 2; v[2] = 3; v[3] = 5; for(n=4,up_to, p = v[n-2]; q = nextprime(1+p); while(q%4 != p%4, q=nextprime(1+q)); v[n] = q); (v); };
    v108546 = A108546list(up_to);
    A108546(n) = v108546[n];
    A108548(n) = { my(f=factor(n)); f[,1] = apply(A108546,apply(primepi,f[,1])); factorback(f); }; \\ Antti Karttunen, Apr 25 2022

Extensions

Name edited by Antti Karttunen, Apr 25 2022

A332893 a(1) = 1, a(2n) = n, a(2n+1) = A332819(2n+1).

Original entry on oeis.org

1, 1, 2, 2, 3, 3, 5, 4, 4, 5, 13, 6, 7, 7, 6, 8, 11, 9, 17, 10, 10, 11, 29, 12, 9, 13, 8, 14, 19, 15, 37, 16, 26, 17, 15, 18, 23, 19, 14, 20, 31, 21, 41, 22, 12, 23, 53, 24, 25, 25, 22, 26, 43, 27, 39, 28, 34, 29, 61, 30, 47, 31, 20, 32, 21, 33, 73, 34, 58, 35, 89, 36, 59, 37, 18, 38, 65, 39, 97, 40, 16, 41, 101, 42, 33, 43, 38, 44, 67, 45, 35
Offset: 1

Views

Author

Antti Karttunen, Mar 01 2020

Keywords

Comments

For any node n >= 2 in binary trees like A332815, a(n) gives the parent node of n.

Crossrefs

Cf. also A252463.

Programs

Formula

a(1) = 1, after which a(n) = n/2 for even n, and a(n) = A332819(n) for odd n.

A332899 a(1) = 0, and for n > 2, a(n) = a(A332893(n)) + A000035(n).

Original entry on oeis.org

0, 1, 2, 1, 3, 2, 4, 1, 2, 3, 6, 2, 5, 4, 3, 1, 7, 2, 8, 3, 4, 6, 10, 2, 3, 5, 2, 4, 9, 3, 12, 1, 6, 7, 4, 2, 11, 8, 5, 3, 13, 4, 14, 6, 3, 10, 16, 2, 4, 3, 7, 5, 15, 2, 6, 4, 8, 9, 18, 3, 17, 12, 4, 1, 5, 6, 20, 7, 10, 4, 22, 2, 19, 11, 3, 8, 6, 5, 24, 3, 2, 13, 26, 4, 7, 14, 9, 6, 21, 3, 5, 10, 12, 16, 8, 2, 23, 4, 6, 3, 25, 7, 28, 5, 4
Offset: 1

Views

Author

Antti Karttunen, Mar 04 2020

Keywords

Comments

a(n) tells how many odd numbers are encountered when map x -> A332893(x) is used to traverse from n to 1, the root of the binary tree A332815. This count includes both the starting n itself if it is odd, but excludes 1 where the iteration ends.
a(n) also gives the index of the largest prime factor (A061395) in A332808(n), which is the inverse permutation of A108548 (see also A108546).

Crossrefs

Cf. A000079 (after its initial term, gives the positions of 1's).

Programs

Formula

a(1) = 0, and for n > 1, a(n) = a(A332893(n)) + A000035(n).
a(n) = A000120(A332811(n)).
a(n) = A061395(A332808(n)).
a(n) = A332897(n) + A332898(n).
a(n) <= A332894(n).
For all n > 1, a(n) = 1 + A080791(A332816(n)).

A332806 Permutation of primes, inverse of A108546.

Original entry on oeis.org

2, 3, 5, 7, 13, 11, 17, 19, 29, 23, 37, 31, 41, 43, 53, 47, 61, 59, 71, 79, 67, 89, 101, 73, 83, 97, 107, 113, 103, 109, 131, 139, 127, 151, 137, 163, 149, 173, 181, 157, 193, 167, 199, 179, 191, 223, 229, 239, 251, 197, 211, 263, 227, 271, 233, 281, 241, 293, 257, 269, 311, 277, 317, 337, 283, 307, 349, 313, 359, 331, 347, 373, 383, 353
Offset: 1

Views

Author

Antti Karttunen, Feb 27 2020

Keywords

Crossrefs

Differs from its inverse A108546 for the first time at n=19, where a(19) = 71, while A108546(19) = 73.

Programs

  • PARI
    up_to = 10000;
    A332806list(up_to) = { my(v=vector(2), xs=Map(), lista=List([]), p,q,u); v[2] = 3; v[1] = 5; mapput(xs,1,1); mapput(xs,2,2); mapput(xs,3,3);  for(n=4,up_to, p = v[2-(n%2)]; q = nextprime(1+p); while(q%4 != p%4, q=nextprime(1+q)); v[2-(n%2)] = q; mapput(xs,primepi(q),n)); for(i=1, oo, if(!mapisdefined(xs, i, &u), return(Vec(lista)), listput(lista, prime(u)))); };
    v332806 = A332806list(up_to);
    A332806(n) = v332806[n];

Formula

a(n) = A000040(A332805(n)).
a(A000720(A108547(n))) = A108547(n).

A332894 a(1) = 0, a(2n) = 1 + a(n), a(2n+1) = 1 + a(A332819(2n+1)); also binary width of terms of A332816.

Original entry on oeis.org

0, 1, 2, 2, 3, 3, 4, 3, 3, 4, 6, 4, 5, 5, 4, 4, 7, 4, 8, 5, 5, 7, 10, 5, 4, 6, 4, 6, 9, 5, 12, 5, 7, 8, 5, 5, 11, 9, 6, 6, 13, 6, 14, 8, 5, 11, 16, 6, 5, 5, 8, 7, 15, 5, 7, 7, 9, 10, 18, 6, 17, 13, 6, 6, 6, 8, 20, 9, 11, 6, 22, 6, 19, 12, 5, 10, 7, 7, 24, 7, 5, 14, 26, 7, 8, 15, 10, 9, 21, 6, 6, 12, 13, 17, 9, 7, 23, 6, 8, 6, 25, 9, 28, 8, 6
Offset: 1

Views

Author

Antti Karttunen, Mar 04 2020

Keywords

Comments

a(n) tells how many iterations of A332893 are needed before 1 is reached, i.e., the distance of n from 1 in binary trees like A332815.
Each n > 0 occurs 2^(n-1) times in total.

Crossrefs

Programs

Formula

a(n) = A252464(A332808(n)).
a(1) = 0, and for n > 1, a(n) = 1 + a(A332893(n)).
For n >= 1, a(A108546(n)) = n; for all n >= 0, a(2^n) = n.
For n > 1: (Start)
a(n) = 1 + a(n/2) if n is even, and a(n) = 1 + a(A332819(n)), if n is odd.
a(n) = A070939(A332816(n)).
a(n) >= A332899(n).
(End)
Showing 1-9 of 9 results.