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 1-10 of 12 results. Next

A277715 Row 5 of A277710: Positions of 5's in A264977; positions of 10's in A277330.

Original entry on oeis.org

9, 21, 45, 93, 189, 381, 657, 765, 873, 1317, 1533, 1749, 2457, 2637, 3069, 3501, 4329, 4917, 5241, 5277, 5745, 6141, 6345, 7005, 8661, 9561, 9837, 10017, 10485, 10557, 11493, 12285, 12693, 14013, 15129, 17325, 17985, 19125, 19677, 20037, 20973, 21117, 21969, 22989, 24573, 25389, 26793, 28029, 30261, 31545, 34653, 35973
Offset: 1

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Author

Antti Karttunen, Oct 29 2016

Keywords

Comments

Positions in A260443 of terms that are ten times a perfect square (terms in A033583, although not all of them are present in A260443).
It seems that A068156 from 9 onward is a subsequence, which (if true) would also be a sufficient condition for this sequence to be infinite.

Crossrefs

Formula

A277716(n) = a(n)/3.

A277824 a(0) = 0; for n >= 1, a(n) = 1 + a(A277815(n)); index of the column where n is located in array A277710.

Original entry on oeis.org

0, 1, 1, 1, 1, 2, 1, 1, 1, 1, 2, 2, 1, 3, 1, 1, 1, 1, 1, 3, 2, 2, 2, 1, 1, 2, 3, 2, 1, 4, 1, 1, 1, 1, 1, 4, 1, 3, 3, 2, 2, 5, 2, 2, 2, 3, 1, 1, 1, 1, 2, 3, 3, 4, 2, 2, 1, 2, 4, 2, 1, 6, 1, 1, 1, 1, 1, 5, 1, 3, 4, 3, 1, 1, 3, 3, 3, 5, 2, 3, 2, 1, 5, 4, 2, 7, 2, 1, 2, 2, 3, 4, 1, 4, 1, 1, 1, 1, 1, 4, 2, 2, 3, 5, 3, 2, 4, 5, 2, 6, 2, 1, 1, 2, 2, 3, 4, 4, 2, 2, 1
Offset: 0

Views

Author

Antti Karttunen, Nov 06 2016

Keywords

Comments

For n >= 1, a(n) = index of the column where n is located in array A277710.
Ordinal transform of A277826 and A277884.

Crossrefs

Cf. A277817 (gives the positions of ones in this sequence).
Cf. A277826, A277884 and their scatter-plots.

Programs

Formula

a(0) = 0; for n >= 1, a(n) = 1 + a(A277815(n)).

A277709 Transpose of square array A277710.

Original entry on oeis.org

1, 2, 5, 3, 10, 13, 4, 39, 26, 29, 9, 20, 75, 58, 41, 6, 21, 52, 147, 82, 61, 7, 78, 45, 116, 207, 122, 85, 8, 11, 150, 93, 164, 291, 170, 125, 81, 40, 19, 294, 189, 244, 411, 250, 173, 18, 105, 104, 35, 414, 381, 340, 579, 346, 209, 23, 42, 165, 232, 67, 582, 657, 500, 819, 418, 253, 12, 43, 90, 213, 328, 131, 822, 765, 692, 927, 506, 281
Offset: 1

Views

Author

Antti Karttunen, Oct 29 2016

Keywords

Comments

See A277710.

Crossrefs

Cf. A277710.

Programs

A264977 a(0) = 0, a(1) = 1, a(2*n) = 2*a(n), a(2*n+1) = a(n) XOR a(n+1).

Original entry on oeis.org

0, 1, 2, 3, 4, 1, 6, 7, 8, 5, 2, 7, 12, 1, 14, 15, 16, 13, 10, 7, 4, 5, 14, 11, 24, 13, 2, 15, 28, 1, 30, 31, 32, 29, 26, 7, 20, 13, 14, 3, 8, 1, 10, 11, 28, 5, 22, 19, 48, 21, 26, 15, 4, 13, 30, 19, 56, 29, 2, 31, 60, 1, 62, 63, 64, 61, 58, 7, 52, 29, 14, 19, 40, 25, 26, 3, 28, 13, 6, 11, 16, 9, 2, 11, 20, 1, 22
Offset: 0

Views

Author

Antti Karttunen, Dec 10 2015

Keywords

Comments

a(n) is the n-th Stern polynomial (cf. A260443, A125184) evaluated at X = 2 over the field GF(2).
For n >= 1, a(n) gives the index of the row where n occurs in array A277710.

Examples

			In this example, binary numbers are given zero-padded to four bits.
a(2) = 2a(1) = 2 * 1 = 2.
a(3) = a(1) XOR a(2) = 1 XOR 2 = 0001 XOR 0010 = 0011 = 3.
a(4) = 2a(2) = 2 * 2 = 4.
a(5) = a(2) XOR a(3) = 2 XOR 3 = 0010 XOR 0011 = 0001 = 1.
a(6) = 2a(3) = 2 * 3 = 6.
a(7) = a(3) XOR a(4) = 3 XOR 4 = 0011 XOR 0100 = 0111 = 7.
		

Crossrefs

Cf. A023758 (the fixed points).
Cf. also A068156, A168081, A265407.
Cf. A277700 (binary weight of terms).
Cf. A277701, A277712, A277713 (positions of 1's, 2's and 3's in this sequence).
Cf. A277711 (position of the first occurrence of each n in this sequence).
Cf. also arrays A277710, A099884.

Programs

  • Mathematica
    recurXOR[0] = 0; recurXOR[1] = 1; recurXOR[n_] := recurXOR[n] = If[EvenQ[n], 2recurXOR[n/2], BitXor[recurXOR[(n - 1)/2 + 1], recurXOR[(n - 1)/2]]]; Table[recurXOR[n], {n, 0, 100}] (* Jean-François Alcover, Oct 23 2016 *)
  • Python
    class Memoize:
        def _init_(self, func):
            self.func=func
            self.cache={}
        def _call_(self, arg):
            if arg not in self.cache:
                self.cache[arg] = self.func(arg)
            return self.cache[arg]
    @Memoize
    def a(n): return n if n<2 else 2*a(n//2) if n%2==0 else a((n - 1)//2)^a((n + 1)//2)
    print([a(n) for n in range(51)]) # Indranil Ghosh, Jul 27 2017

Formula

a(0) = 0, a(1) = 1, a(2*n) = 2*a(n), a(2*n+1) = a(n) XOR a(n+1).
a(n) = A248663(A260443(n)).
a(n) = A048675(A277330(n)). - Antti Karttunen, Oct 27 2016
Other identities. For all n >= 0:
a(n) = n - A265397(n).
From Antti Karttunen, Oct 28 2016: (Start)
A000035(a(n)) = A000035(n). [Preserves the parity of n.]
A010873(a(n)) = A010873(n). [a(n) mod 4 = n mod 4.]
A001511(a(n)) = A001511(n) = A055396(A277330(n)). [In general, the 2-adic valuation of n is preserved.]
A010060(a(n)) = A011655(n).
a(n) <= n.
For n >= 2, a((2^n)+1) = (2^n) - 3.
The following two identities are so far unproved:
For n >= 2, a(3*A000225(n)) = a(A068156(n)) = 5.
For n >= 2, a(A068156(n)-2) = A062709(n) = 2^n + 3.
(End)

A277330 a(0)=1, a(1)=2, a(2n) = A003961(a(n)), a(2n+1) = lcm(a(n),a(n+1))/gcd(a(n),a(n+1)).

Original entry on oeis.org

1, 2, 3, 6, 5, 2, 15, 30, 7, 10, 3, 30, 35, 2, 105, 210, 11, 70, 21, 30, 5, 10, 105, 42, 77, 70, 3, 210, 385, 2, 1155, 2310, 13, 770, 231, 30, 55, 70, 105, 6, 7, 2, 21, 42, 385, 10, 165, 66, 143, 110, 231, 210, 5, 70, 1155, 66, 1001, 770, 3, 2310, 5005, 2, 15015, 30030, 17, 10010, 3003, 30, 715, 770, 105, 66, 91, 154, 231, 6, 385, 70, 15, 42, 11, 14, 3, 42, 55, 2
Offset: 0

Views

Author

Antti Karttunen, Oct 27 2016

Keywords

Comments

Each term is a squarefree number, A005117.

Crossrefs

Cf. A023758 (positions where coincides with A260443).
Cf. A277701, A277712, A277713 for the positions of 2's, 3's and 6's in this sequence, which are also the first three rows of array A277710.
Cf. also A255483.

Formula

a(0) = 1, a(1) = 2, a(2n) = A003961(a(n)), a(2n+1) = lcm(a(n),a(n+1))/gcd(a(n),a(n+1)).
Other identities. For all n >= 0:
a(n) = A007913(A260443(n)).
a(n) = A019565(A264977(n)), A048675(a(n)) = A264977(n).
A055396(a(n)) = A277707(A260443(n)) = A001511(n).

A277701 Positions of ones in A264977; positions of twos in A277330.

Original entry on oeis.org

1, 5, 13, 29, 41, 61, 85, 125, 173, 209, 253, 281, 313, 349, 421, 509, 565, 629, 701, 845, 929, 1021, 1133, 1261, 1405, 1693, 1861, 2045, 2269, 2525, 2665, 2813, 3121, 3313, 3389, 3725, 3905, 4093, 4541, 4841, 5053, 5209, 5257, 5333, 5629, 5993, 6245, 6629, 6781, 7453, 7813, 8189, 8537, 9085, 9593, 9685, 9905, 10109, 10421, 10517, 10669, 10921
Offset: 1

Views

Author

Antti Karttunen, Oct 27 2016

Keywords

Comments

Positions in A260443 of terms that are twice square (terms in A001105, although not all of them are present in A260443).

Crossrefs

Row 1 of A277710.
Cf. also A277712, A277713.

Formula

A277712(n) = 2*a(n) for all n >= 1.

A277713 Positions of 3's in A264977; positions of 6's in A277330.

Original entry on oeis.org

3, 39, 75, 147, 207, 291, 411, 579, 819, 927, 1155, 1635, 1851, 2307, 2487, 2583, 2919, 3267, 3699, 3903, 4611, 4971, 5163, 5835, 6531, 7395, 7803, 9219, 9939, 10323, 10839, 11667, 13059, 14787, 15603, 15999, 17895, 18435, 19875, 20295, 20643, 21675, 23331, 26115, 29571, 31203, 31995, 33327, 34383, 35787, 36867, 39747, 40587, 41283, 43347
Offset: 1

Views

Author

Antti Karttunen, Oct 28 2016

Keywords

Comments

Positions in A260443 of terms that are six times a perfect square (terms in A033581, although not all of them are present in A260443).
All terms are multiples of three.

Crossrefs

Formula

A277714(n) = a(n)/3.

A277712 Positions of 2's in A264977; positions of 3's in A277330.

Original entry on oeis.org

2, 10, 26, 58, 82, 122, 170, 250, 346, 418, 506, 562, 626, 698, 842, 1018, 1130, 1258, 1402, 1690, 1858, 2042, 2266, 2522, 2810, 3386, 3722, 4090, 4538, 5050, 5330, 5626, 6242, 6626, 6778, 7450, 7810, 8186, 9082, 9682, 10106, 10418, 10514, 10666, 11258, 11986, 12490, 13258, 13562, 14906, 15626, 16378, 17074, 18170, 19186, 19370, 19810
Offset: 1

Views

Author

Antti Karttunen, Oct 28 2016

Keywords

Comments

Positions in A260443 of terms that are three times a perfect square (terms in A033428, although not all of them are present in A260443).

Crossrefs

Row 2 of A277710.
Cf. also A277713.

Formula

a(n) = 2*A277701(n).

A277696 Permutation of natural numbers: a(1) = 1; a(2n) = A277817(1+a(n)), a(2n+1) = A277816(a(n)).

Original entry on oeis.org

1, 2, 5, 3, 10, 7, 13, 4, 39, 15, 26, 9, 11, 18, 29, 6, 20, 92, 75, 24, 27, 49, 58, 14, 21, 16, 19, 31, 42, 62, 41, 8, 78, 33, 52, 270, 172, 196, 147, 47, 312, 56, 51, 126, 101, 143, 82, 23, 22, 34, 45, 28, 80, 32, 35, 64, 59, 96, 90, 153, 118, 95, 61, 12, 40, 224, 150, 66, 57, 129, 116, 1134, 534, 606, 316, 752, 404, 520, 207, 120, 55, 1400, 600
Offset: 1

Views

Author

Antti Karttunen, Nov 06 2016

Keywords

Comments

This sequence can be represented as a binary tree. Each left hand child is produced as A277817(1+n), and each right hand child as A277816(n), when the parent node contains n:
1
................../ \..................
2 5
3......../ \........10 7......../ \........13
/ \ / \ / \ / \
/ \ / \ / \ / \
/ \ / \ / \ / \
4 39 15 26 9 11 18 29
6 20 92 75 24 27 49 58 14 21 16 19 31 42 62 41
etc.

Crossrefs

Inverse: A277695.
Cf. A277701 (the rightmost edge of the tree).

Formula

a(1) = 1; and then after, a(2n) = A277817(1+a(n)), a(2n+1) = A277816(a(n)).

A277816 a(n) = the least k > n for which A264977(k) = A264977(n), or 0 if no such k exists.

Original entry on oeis.org

0, 5, 10, 39, 20, 13, 78, 11, 40, 21, 26, 19, 156, 29, 22, 27, 80, 25, 42, 35, 52, 45, 38, 43, 312, 37, 58, 51, 44, 41, 54, 59, 160, 57, 50, 67, 84, 53, 70, 75, 104, 61, 90, 79, 76, 93, 86, 55, 624, 101, 74, 99, 116, 77, 102, 71, 88, 69, 82, 115, 108, 85, 118, 123, 320, 121, 114, 131, 100, 117, 134, 91, 168, 89, 106, 147, 140, 109, 150, 83, 208, 105
Offset: 0

Views

Author

Antti Karttunen, Nov 06 2016

Keywords

Crossrefs

Cf. A277815 (a left inverse).
Cf. A277701, A277712, A277713, A277715 (iterates of this sequence starting from 1, 2, 3 and 9 respectively).

Programs

  • Scheme
    (define (A277816 n) (if (zero? n) n (let ((v (A264977 n))) (let loop ((k (+ 1 n))) (if (= v (A264977 k)) k (loop (+ 1 k)))))))

Formula

For all n >= 0, A277815(a(n)) = n.
Showing 1-10 of 12 results. Next