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.

Previous Showing 11-20 of 20 results.

A284011 a(n) = least natural number with the same prime signature Stern polynomial B(n,x) has when it is factored over Z.

Original entry on oeis.org

1, 2, 2, 4, 2, 6, 2, 8, 4, 6, 2, 12, 2, 6, 6, 16, 2, 12, 2, 12, 6, 6, 2, 24, 2, 6, 8, 12, 2, 30, 2, 32, 6, 6, 6, 36, 2, 6, 6, 24, 2, 30, 2, 12, 12, 6, 2, 48, 4, 6, 6, 12, 2, 24, 2, 24, 6, 6, 2, 60, 2, 6, 30, 64, 2, 30, 2, 12, 6, 30, 2, 72, 2, 6, 12, 12, 2, 30, 2, 48, 6, 6, 2, 60, 6, 6, 6, 24, 2, 60, 2, 12, 6, 6, 2, 96, 2, 12, 12, 12, 2, 30, 2, 24, 30, 6, 2, 72
Offset: 1

Views

Author

Antti Karttunen, Mar 20 2017

Keywords

Examples

			B_9(x) = x^2 + 2x + 1, which factorizes as (x + 1)^2, thus a(9) = 2^2 = 4.
		

Crossrefs

Cf. A046523, A125184, A186891 (positions of terms <= 2), A260443, A277013, A284010, A284012.
Cf. also A278233, A278243.
Differs from A046523 for the first time at n=25, where a(25) = 2, while A046523(25) = 4.

Programs

  • PARI
    \\ After Charles R Greathouse IV's code in A046523 and A186891:
    ps(n) = if(n<2, n, if(n%2, ps(n\2)+ps(n\2+1), 'x*ps(n\2)));
    A284011(n) = { my(p=0, f=vecsort(factor(ps(n))[, 2], ,4)); prod(i=1, #f, (p=nextprime(p+1))^f[i]); }
    for(n=1, 16384, write("b284011.txt", n, " ", A284011(n)));

Formula

a(1) = 1 (by convention), and for n > 1, a(n) = A284010(A260443(n)).

A304751 Filter sequence: Restricted growth sequence transform of function that gives the least natural number with the same prime signature that (0,1)-polynomial encoded in the binary expansion of n has when it is factored over Q.

Original entry on oeis.org

1, 2, 2, 3, 2, 4, 2, 5, 4, 4, 2, 6, 2, 4, 4, 7, 2, 8, 2, 6, 4, 4, 2, 9, 2, 4, 6, 6, 2, 8, 2, 10, 4, 4, 4, 11, 2, 4, 4, 9, 2, 8, 2, 6, 8, 4, 2, 12, 4, 4, 4, 6, 2, 11, 2, 9, 4, 4, 2, 11, 2, 4, 8, 13, 4, 8, 2, 6, 2, 8, 2, 14, 2, 4, 8, 6, 2, 8, 2, 12, 2, 4, 2, 11, 4, 4, 2, 9, 2, 15, 2, 6, 4, 4, 4, 16, 2, 8, 6, 6, 2, 8, 2, 9, 8
Offset: 1

Views

Author

Antti Karttunen, Jun 08 2018

Keywords

Crossrefs

Cf. A206719, A206074 (gives the positions of 2's), A257000.

Programs

  • PARI
    up_to = 65537;
    rgs_transform(invec) = { my(occurrences = Map(), outvec = vector(length(invec)), u=1); for(i=1, length(invec), if(mapisdefined(occurrences,invec[i]), my(pp = mapget(occurrences, invec[i])); outvec[i] = outvec[pp] , mapput(occurrences,invec[i],i); outvec[i] = u; u++ )); outvec; };
    Aux304751(n) = { my(p=0, f=vecsort((factor(Pol(binary(n)))[, 2]), , 4)); prod(i=1, #f, (p=nextprime(p+1))^f[i]); }
    v304751 = rgs_transform(vector(up_to,n,Aux304751(n)));
    A304751(n) = v304751[n];

Formula

For all i, j: a(i) = a(j) => A206719(i) = A206719(j).
For all i, j: a(i) = a(j) => A257000(i) = A257000(j).

A305815 Restricted growth sequence transform of A305814, a filter sequence constructed from the GF(2)[X]-factorization signatures of the divisors of n.

Original entry on oeis.org

1, 2, 2, 3, 4, 5, 2, 6, 7, 8, 2, 9, 2, 5, 6, 10, 11, 12, 2, 13, 14, 5, 15, 16, 3, 5, 17, 9, 15, 16, 2, 18, 5, 19, 20, 21, 2, 5, 22, 23, 2, 24, 15, 9, 25, 26, 2, 27, 7, 9, 28, 9, 15, 29, 14, 16, 22, 26, 2, 30, 2, 5, 9, 31, 32, 33, 2, 34, 20, 35, 15, 36, 2, 5, 37, 9, 5, 38, 15, 39, 40, 5, 41, 42, 43, 26, 5, 16, 15, 44, 45, 46, 5, 5, 8, 47, 2, 12, 48, 49, 41, 50
Offset: 1

Views

Author

Antti Karttunen, Jun 11 2018

Keywords

Crossrefs

Programs

  • PARI
    \\ Needs also code from A305788:
    up_to = 65537;
    rgs_transform(invec) = { my(occurrences = Map(), outvec = vector(length(invec)), u=1); for(i=1, length(invec), if(mapisdefined(occurrences,invec[i]), my(pp = mapget(occurrences, invec[i])); outvec[i] = outvec[pp] , mapput(occurrences,invec[i],i); outvec[i] = u; u++ )); outvec; };
    A305814(n) = { my(m=1); fordiv(n, d, if(d>1, m *= prime(A305788(d)-1))); (m); };
    v305815 = rgs_transform(vector(up_to, n, A305814(n)));
    A305815(n) = v305815[n];

Formula

For all i, j:
a(i) = a(j) => A000005(i) = A000005(j).
a(i) = a(j) => A294883(i) = A294883(j).
a(i) = a(j) => A294884(i) = A294884(j).

A286601 a(n) = A278222(A193231(n)).

Original entry on oeis.org

1, 2, 4, 2, 6, 2, 4, 8, 16, 8, 4, 12, 6, 12, 6, 2, 6, 2, 6, 12, 6, 30, 24, 12, 16, 32, 24, 8, 36, 12, 4, 12, 36, 12, 4, 12, 36, 72, 60, 12, 16, 48, 64, 32, 24, 8, 24, 72, 6, 12, 6, 2, 24, 12, 6, 30, 60, 12, 24, 48, 6, 30, 60, 30, 210, 30, 60, 120, 6, 30, 60, 30, 60, 180, 60, 12, 96, 48, 24, 120, 6, 30, 24, 12, 6, 2, 6, 12, 60, 30, 6, 30
Offset: 0

Views

Author

Antti Karttunen, Jun 04 2017

Keywords

Crossrefs

Cf. A193231, A234022, A278222, A278231, A278233, A286602 (rgs-version of this sequence).

Programs

Formula

a(n) = A278222(A193231(n)).

A304529 a(1) = 0, a(2n) = n, a(2n+1) = a(A305422(2n+1)).

Original entry on oeis.org

0, 1, 1, 2, 2, 3, 1, 4, 3, 5, 1, 6, 1, 7, 4, 8, 8, 9, 1, 10, 2, 11, 11, 12, 1, 13, 6, 14, 7, 15, 1, 16, 25, 17, 7, 18, 1, 19, 14, 20, 1, 21, 19, 22, 12, 23, 1, 24, 3, 25, 16, 26, 13, 27, 1, 28, 22, 29, 1, 30, 1, 31, 5, 32, 10, 33, 1, 34, 2, 35, 59, 36, 1, 37, 44, 38, 55, 39, 13, 40, 2, 41, 9, 42, 32, 43, 1, 44, 47, 45, 1, 46, 19, 47, 26, 48, 1, 49, 50, 50
Offset: 1

Views

Author

Antti Karttunen, Jun 10 2018

Keywords

Comments

This is GF(2)[X] analog of A246277.
For all i, j: a(i) = a(j) => A278233(i) = A278233(j).
For all i, j: a(i) = a(j) => A305788(i) = A305788(j).

Crossrefs

Cf. A014580 (positions of 1's), A278233, A305788.
Cf. also A246277.

Programs

  • PARI
    A091225(n) = polisirreducible(Pol(binary(n))*Mod(1, 2));
    A305419(n) = if(n<3,1, my(k=n-1); while(k>1 && !A091225(k),k--); (k));
    A305422(n) = { my(f = subst(lift(factor(Pol(binary(n))*Mod(1, 2))),x,2)); for(i=1,#f~,f[i,1] = Pol(binary(A305419(f[i,1])))); fromdigits(Vec(factorback(f))%2,2); };
    A304529(n) = if(1==n,0,while(n%2, n = A305422(n)); n/2);

Formula

a(1) = 0, a(2n) = n, a(2n+1) = a(A305422(2n+1)).

A305813 Restricted growth sequence transform of A305812, a filter sequence constructed from the GF(2)[X]-factorization signatures of the proper divisors of n.

Original entry on oeis.org

1, 2, 2, 3, 2, 4, 2, 5, 3, 5, 2, 6, 2, 4, 5, 7, 2, 8, 2, 9, 4, 4, 2, 10, 11, 4, 12, 6, 2, 10, 2, 13, 4, 14, 5, 15, 2, 4, 4, 16, 2, 17, 2, 6, 18, 12, 2, 19, 3, 20, 14, 6, 2, 21, 5, 10, 4, 12, 2, 22, 2, 4, 6, 23, 5, 24, 2, 25, 12, 26, 2, 27, 2, 4, 28, 6, 4, 29, 2, 30, 31, 4, 2, 32, 33, 12, 12, 10, 2, 34, 4, 35, 4, 4, 5, 36, 2, 8, 8, 37, 2, 38, 2, 10, 39
Offset: 1

Views

Author

Antti Karttunen, Jun 11 2018

Keywords

Crossrefs

Programs

  • PARI
    \\ Needs also code from A305788:
    up_to = 65537;
    rgs_transform(invec) = { my(occurrences = Map(), outvec = vector(length(invec)), u=1); for(i=1, length(invec), if(mapisdefined(occurrences,invec[i]), my(pp = mapget(occurrences, invec[i])); outvec[i] = outvec[pp] , mapput(occurrences,invec[i],i); outvec[i] = u; u++ )); outvec; };
    A305812(n) = if(1==n,0, my(m=1); fordiv(n,d,if((d>1)&&(dA305788(d)-1))); (m));
    v305813 = rgs_transform(vector(up_to, n, A305812(n)));
    A305813(n) = v305813[n];

Formula

For all i, j:
a(i) = a(j) => A000005(i) = A000005(j).
a(i) = a(j) => A294881(i) = A294881(j).
a(i) = a(j) => A294882(i) = A294882(j).

A278231 Least number with the same prime signature as the n-th number in Blue-code: a(n) = A046523(A193231(n)).

Original entry on oeis.org

1, 2, 2, 2, 4, 6, 2, 6, 6, 12, 2, 6, 2, 4, 8, 2, 16, 12, 2, 12, 6, 2, 6, 30, 2, 2, 12, 8, 6, 24, 4, 6, 12, 48, 4, 24, 6, 2, 12, 60, 2, 12, 6, 6, 24, 6, 2, 6, 6, 6, 32, 6, 6, 36, 2, 12, 12, 6, 2, 24, 2, 2, 30, 6, 60, 6, 6, 48, 16, 2, 6, 60, 6, 2, 24, 6, 6, 12, 6, 12, 6, 2, 30, 6, 64, 30, 2, 12, 6, 72, 2, 30, 2
Offset: 1

Views

Author

Antti Karttunen, Nov 16 2016

Keywords

Crossrefs

Programs

Formula

a(n) = A046523(A193231(n)).

A305812 a(1) = 0; for n > 1, a(n) = Product_{d|n, 1 < d < n} prime(A305788(d)-1).

Original entry on oeis.org

0, 1, 1, 2, 1, 4, 1, 6, 2, 6, 1, 60, 1, 4, 6, 42, 1, 100, 1, 198, 4, 4, 1, 4620, 3, 4, 10, 60, 1, 4620, 1, 546, 4, 26, 6, 56100, 1, 4, 4, 26334, 1, 600, 1, 60, 210, 10, 1, 1381380, 2, 132, 26, 60, 1, 18700, 6, 4620, 4, 10, 1, 66625020, 1, 4, 60, 15834, 6, 1000, 1, 2418, 10, 3300, 1, 334187700, 1, 4, 84, 60, 4, 2200, 1, 14036022, 110, 4, 1
Offset: 1

Views

Author

Antti Karttunen, Jun 11 2018

Keywords

Crossrefs

Cf. A008578, A278233, A305788, A305813 (rgs-transform), A305814.
Cf. also A305792, A304102.

Programs

  • PARI
    A305812(n) = if(1==n,0, my(m=1); fordiv(n,d,if((d>1)&&(dA305788(d)-1))); (m)); \\ Needs also code from A305788.

Formula

a(1) = 0; for n > 1, a(n) = Product_{d|n, dA008578(A305788(d)).

A305814 a(n) = Product_{d|n, d>1} prime(A305788(d)-1).

Original entry on oeis.org

1, 2, 2, 6, 3, 20, 2, 42, 10, 66, 2, 660, 2, 20, 42, 546, 13, 1700, 2, 3762, 12, 20, 5, 106260, 6, 20, 110, 660, 5, 106260, 2, 15834, 20, 806, 30, 2075700, 2, 20, 44, 1079694, 2, 6600, 5, 660, 4830, 170, 2, 42822780, 10, 660, 754, 660, 5, 691900, 12, 106260, 44, 170, 2, 2731625820, 2, 20, 660, 680862, 114, 17000, 2, 113646, 30, 56100, 5
Offset: 1

Views

Author

Antti Karttunen, Jun 11 2018

Keywords

Crossrefs

Cf. A008578, A278233, A305788, A305812, A305815 (rgs-transform).

Programs

  • PARI
    A305814(n) = { my(m=1); fordiv(n, d, if(d>1, m *= prime(A305788(d)-1))); (m); }; \\ Needs also code from A305788.

Formula

a(n) = Product_{d|n} A008578(A305788(d)).

A305903 Filter sequence for all such sequences b, for which b(A014580(k)) = constant for all k >= 3.

Original entry on oeis.org

1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 7, 11, 7, 12, 13, 14, 15, 16, 7, 17, 18, 19, 20, 21, 7, 22, 23, 24, 25, 26, 7, 27, 28, 29, 30, 31, 7, 32, 33, 34, 7, 35, 36, 37, 38, 39, 7, 40, 41, 42, 43, 44, 45, 46, 7, 47, 48, 49, 7, 50, 7, 51, 52, 53, 54, 55, 7, 56, 57, 58, 59, 60, 7, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 7, 74, 75, 76, 7, 77, 78, 79, 80, 81, 7
Offset: 1

Views

Author

Antti Karttunen, Jun 14 2018

Keywords

Comments

Restricted growth sequence transform of A305900(A091203(n)).
This is GF(2)[X] analog of A305900.
For all i, j:
a(i) = a(j) => A304529(i) = A304529(j) => A305788(i) = A305788(j).
a(i) = a(j) => A268389(i) = A268389(j).

Crossrefs

Programs

  • PARI
    up_to = 1000;
    A091225(n) = polisirreducible(Pol(binary(n))*Mod(1, 2));
    prepare_v091226(up_to) = { my(v = vector(up_to), c=0); for(i=1,up_to,c += A091225(i); v[i] = c); (v); }
    v091226 = prepare_v091226(up_to);
    A091226(n) = if(!n,n,v091226[n]);
    A305903(n) = if(n<7,n,if(A091225(n),7,3+n-A091226(n)));

Formula

For n < 7, a(n) = n, for >= 7, a(n) = 7 when n is in A014580[3..] (= 7, 11, 13, 19, 25, 31, ...), and a(n) = 3+n-A091226(n) when n is in A091242[4..] (= 8, 9, 10, 12, 14, 15, ...).
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