A001511 -id:A001511 - cp's OEIS frontend

A183036 G.f.: exp( Sum_{n>=1} A001511(n)2^A001511(n)x^n/n ) where A001511(n) equals the 2-adic valuation of 2n.

1, 2, 6, 10, 24, 38, 74, 110, 200, 290, 486, 682, 1096, 1510, 2314, 3118, 4650, 6182, 8946, 11710, 16616, 21522, 29886, 38250, 52328, 66406, 89394, 112382, 149496, 186610, 245086, 303562, 394814, 486066, 625686, 765306, 977112, 1188918, 1504954

Offset: 0

Paul D. Hanna, Dec 19 2010

nonn

Compare to B(x), the g.f. of the binary partitions (A000123):
B(x) = exp( Sum_{n>=1} 2^A001511(n)*x^n/n ) = (1-x)^(-1)*Product_{n>=0} 1/(1 - x^(2^n)).
2^A001511(n) exactly divides 2n.

			G.f.: A(x) = 1 + 2*x + 6*x^2 + 10*x^3 + 24*x^4 + 38*x^5 + 74*x^6 +...
log(A(x)) = 2*x + 8*x^2/2 + 2*x^3/3 + 24*x^4/4 + 2*x^5/5 + 8*x^6/6 + 2*x^7/7 + 64*x^8/8 + 2*x^9/9 + 8*x^10/10 +...+ A183037(n)*x^n/n +...

Cf. A183037, A183038, A001511, A000123.

{a(n)=polcoeff(exp(sum(m=1,n,valuation(2*m,2)*2^valuation(2*m,2)*x^m/m)+x*O(x^n)),n)}

G.f. satisfies: A(x) = (1-x^2)/(1-x)^2 * A(x^2)^2/A(x^4).

A183037 a(n) = A001511(n)*2^A001511(n) where A001511(n) equals the 2-adic valuation of 2n.

Original entry on oeis.org

2, 8, 2, 24, 2, 8, 2, 64, 2, 8, 2, 24, 2, 8, 2, 160, 2, 8, 2, 24, 2, 8, 2, 64, 2, 8, 2, 24, 2, 8, 2, 384, 2, 8, 2, 24, 2, 8, 2, 64, 2, 8, 2, 24, 2, 8, 2, 160, 2, 8, 2, 24, 2, 8, 2, 64, 2, 8, 2, 24, 2, 8, 2, 896, 2, 8, 2, 24, 2, 8, 2, 64, 2, 8, 2, 24, 2, 8, 2, 160, 2, 8, 2, 24, 2, 8, 2, 64, 2, 8, 2, 24, 2

Offset: 1

Paul D. Hanna, Dec 19 2010

nonn

2n/2^A001511(n) is odd for n >= 1, so that A001511(n) is logarithmic in nature.

			L.g.f.: A(x) = 2*x + 8*x^2/2 + 2*x^3/3 + 24*x^4/4 + 2*x^5/5 + 8*x^6/6 + 2*x^7/7 + 64*x^8/8 + 2*x^9/9 + 8*x^10/10 + ...
The g.f. of A183036 begins:
exp(A(x)) = 1 + 2*x + 6*x^2 + 10*x^3 + 24*x^4 + 38*x^5 + 74*x^6 + ...

Antti Karttunen, Table of n, a(n) for n = 1..16383

Cf. A183036.

Array[# 2^# &[IntegerExponent[#, 2] + 1] &, 93] (* Michael De Vlieger, Nov 06 2018 *)

{a(n)=valuation(2*n,2)*2^valuation(2*n,2)}

def A183037(n): return (m:=n&-n)*m.bit_length()<<1 # Chai Wah Wu, Jul 12 2022

Logarithmic derivative of A183036.

A217553 G.f.: exp( Sum_{n>=1} 4^A001511(n) * x^n/n ), where 2^A001511(n) is the highest power of 2 that divides 2*n.

Original entry on oeis.org

1, 4, 16, 44, 128, 308, 752, 1628, 3584, 7268, 14864, 28556, 55296, 102036, 189168, 337084, 603136, 1044676, 1814288, 3064556, 5188352, 8578548, 14205936, 23041308, 37420800, 59680548, 95265552, 149620812, 235161216, 364301652, 564627952, 863725948, 1321756672

Offset: 0

Paul D. Hanna, Oct 30 2012

nonn

Compare g.f. to the g.f. of binary partitions (A000123):

exp( Sum_{n>=1} 2^A001511(n) * x^n/n ).

			G.f.: A(x) = 1 + 4*x + 16*x^2 + 44*x^3 + 128*x^4 + 308*x^5 + 752*x^6 +...
where
log(A(x)) = 4^1*x + 4^2*x^2/2 + 4^1*x^3/3 + 4^4*x^4/4 + 4^1*x^5/5 + 4^2*x^6/6 + 4^1*x^7/7 + 4^4*x^8/8 + 4^1*x^9/9 + 4^2*x^10/10 + 4^1*x^11/11 + 4^4*x^12/12 +...+ 4^A001511(n)*x^n/n +...

Cf. A162581, A180591, A001511.

{a(n)=polcoeff(exp(sum(m=1,n,4^valuation(2*m,2)*x^m/m)+x*O(x^n)),n)}
for(n=0,31,print1(a(n),", "))

Self-convolution of A162581.

A253790 a(1) = 1; thereafter, odd numbers such that A055396(n) = A001511(n-1).

Original entry on oeis.org

1, 3, 5, 15, 27, 39, 51, 63, 75, 85, 87, 99, 111, 123, 125, 135, 147, 159, 171, 183, 195, 205, 207, 209, 217, 219, 231, 243, 245, 255, 267, 279, 291, 303, 315, 325, 327, 329, 339, 351, 363, 365, 375, 387, 399, 411, 423, 435, 445, 447, 459, 471, 481, 483, 485, 495, 507, 519, 531, 543, 553, 555

Offset: 1

Antti Karttunen, Jan 13 2015

nonn

After 1, all such odd numbers whose smallest prime factor A020639(n) = A000040(k+1), where k = A007814(n-1), the 2-adic valuation of the preceding even number.

Any odd number present in A253789 must be one of these terms.

Antti Karttunen, Table of n, a(n) for n = 1..10000

Cf. A000040, A001511, A007814, A020639, A029747, A055396, A253789.

A286367 Compound filter: a(n) = P(A001511(n), A286364(n)), where P(n,k) is sequence A000027 used as a pairing function.

Original entry on oeis.org

1, 3, 2, 6, 4, 5, 2, 10, 22, 8, 2, 9, 4, 5, 11, 15, 4, 30, 2, 13, 121, 5, 2, 14, 46, 8, 407, 9, 4, 17, 2, 21, 121, 8, 11, 39, 4, 5, 11, 19, 4, 138, 2, 9, 67, 5, 2, 20, 22, 57, 11, 13, 4, 437, 11, 14, 121, 8, 2, 24, 4, 5, 2212, 28, 211, 138, 2, 13, 121, 17, 2, 49, 4, 8, 92, 9, 121, 17, 2, 26, 7261, 8, 2, 156, 211, 5, 11, 14, 4, 80, 11, 9, 121, 5, 11, 27, 4, 30

Offset: 1

Antti Karttunen, May 08 2017

nonn

This sequence contains, in addition to the information contained in A286364 (which packs the values of A286361(n) and A286363(n) to a single value with the pairing function A000027), also the highest power of 2 dividing n. Note that this is more information than A286365, as it stores only the parity of the exponent of 2.

For all i, j: a(i) = a(j) => A286161(i) = A286161(j).

Antti Karttunen, Table of n, a(n) for n = 1..10000
Eric Weisstein's World of Mathematics, Pairing Function

Cf. A000027, A001511, A286161, A286361, A286363, A286364, A286365.

from sympy import factorint
from operator import mul
def P(n):
    f = factorint(n)
    return sorted([f[i] for i in f])
def a046523(n):
    x=1
    while True:
        if P(n) == P(x): return x
        else: x+=1
def A(n, k):
    f = factorint(n)
    return 1 if n == 1 else reduce(mul, [1 if i%4==k else i**f[i] for i in f])
def T(n, m): return ((n + m)**2 - n - 3*m + 2)/2
def a286364(n): return T(a046523(n/A(n, 1)), a046523(n/A(n, 3)))
def a001511(n): return 2 + bin(n - 1)[2:].count("1") - bin(n)[2:].count("1")
def a(n): return T(a001511(n), a286364(n)) # Indranil Ghosh, May 09 2017

(define (A286367 n) (* (/ 1 2) (+ (expt (+ (A001511 n) (A286364 n)) 2) (- (A001511 n)) (- (* 3 (A286364 n))) 2)))

a(n) = (1/2)*(2 + ((A001511(n)+A286364(n))^2) - A001511(n) - 3*A286364(n)).

A286451 Compound filter (2-adic valuation of sigma(n) & 2-adic valuation of n): a(n) = P(A286357(n), A001511(n)), where P(n,k) is sequence A000027 used as a pairing function, with a(1) = 0 by an explicit convention.

Original entry on oeis.org

0, 2, 6, 4, 3, 9, 10, 7, 1, 5, 6, 13, 3, 14, 10, 11, 3, 2, 6, 8, 21, 9, 10, 18, 1, 5, 10, 19, 3, 14, 21, 16, 15, 5, 15, 4, 3, 9, 10, 12, 3, 27, 6, 13, 3, 14, 15, 24, 1, 2, 10, 8, 3, 14, 10, 25, 15, 5, 6, 19, 3, 27, 10, 22, 6, 20, 6, 8, 21, 20, 10, 7, 3, 5, 6, 13, 21, 14, 15, 17, 1, 5, 6, 34, 6, 9, 10, 18, 3, 5, 15, 19, 36, 20, 10, 31, 3, 2, 6, 4, 3, 14, 10

Offset: 1

Antti Karttunen, May 13 2017

nonn

Antti Karttunen, Table of n, a(n) for n = 1..10000
Eric Weisstein's World of Mathematics, Pairing Function

Cf. A000027, A001511, A286357, A286260, A286358.

A001511(n) = (1+valuation(n,2));
A286357(n) = A001511(sigma(n));
A286451(n) = if(1==n,0,(1/2)*(2 + ((A286357(n)+A001511(n))^2) - A286357(n) - 3*A001511(n)));
for(n=1, 10000, write("b286451.txt", n, " ", A286451(n)));

from sympy import divisor_sigma as D
def T(n, m): return ((n + m)**2 - n - 3*m + 2)/2
def a001511(n): return bin(n)[2:][::-1].index("1") + 1
def a(n): return 0 if n==1 else T(a001511(D(n)), a001511(n)) # Indranil Ghosh, May 14 2017

(define (A286451 n) (if (= 1 n) 0 (* (/ 1 2) (+ (expt (+ (A286357 n) (A001511 n)) 2) (- (A286357 n)) (- (* 3 (A001511 n))) 2))))

a(1) = 0; for n > 1, a(n) = (1/2)*(2 + ((A286357(n)+A001511(n))^2) - A286357(n) - 3*A001511(n)).

A286461 Compound filter (2-adic valuation of n & 4k+1,4k+3 prime-signature combination of 2n-1): a(n) = P(A001511(n), A286364((2*n)-1)), where P(n,k) is sequence A000027 used as a pairing function.

Original entry on oeis.org

1, 5, 4, 9, 22, 5, 4, 32, 4, 5, 121, 9, 46, 437, 4, 20, 121, 17, 4, 24, 4, 5, 67, 14, 22, 17, 4, 24, 121, 5, 4, 2562, 211, 5, 121, 9, 4, 107, 121, 14, 7261, 5, 211, 24, 4, 17, 121, 41, 4, 2280, 4, 9, 254, 5, 4, 32, 4, 17, 67, 24, 22, 17, 631, 35, 121, 5, 121, 783, 4, 5, 121, 32, 211, 2280, 4, 9, 67, 17, 4, 41, 121, 5, 254, 9, 46, 2280, 4, 140, 121, 5, 4, 24

Offset: 1

Antti Karttunen, May 10 2017

nonn

Antti Karttunen, Table of n, a(n) for n = 1..10000
Eric Weisstein's World of Mathematics, Pairing Function
Indranil Ghosh, Python program to generate the sequence

Cf. A000027, A001511, A046523, A278223, A286161, A286364, A286371, A286372, A286463, A286465.

(define (A286461 n) (* (/ 1 2) (+ (expt (+ (A001511 n) (A286364 (+ n n -1))) 2) (- (A001511 n)) (- (* 3 (A286364 (+ n n -1)))) 2)))

a(n) = (1/2)*(2 + ((A001511(n)+A286364((2*n)-1))^2) - A001511(n) - 3*A286364((2*n)-1)).

A286595 Compound filter (2-adic valuation & deficiency/abundance): a(n) = P(A001511(n), A286449(n)), where P(n,k) is sequence A000027 used as a pairing function.

Original entry on oeis.org

1, 3, 2, 6, 4, 12, 11, 10, 16, 5, 22, 48, 37, 8, 11, 15, 46, 68, 67, 108, 22, 107, 106, 175, 137, 30, 154, 18, 172, 138, 191, 21, 67, 173, 106, 256, 232, 57, 106, 329, 277, 138, 301, 13, 37, 353, 352, 501, 407, 467, 191, 24, 466, 138, 497, 634, 562, 632, 631, 744, 704, 192, 106, 28, 352, 138, 742, 39, 301, 38, 781, 950, 862, 597, 596, 58, 631, 138, 904, 1133, 407

Offset: 1

Antti Karttunen, May 21 2017

nonn

Antti Karttunen, Table of n, a(n) for n = 1..10000
Eric Weisstein's World of Mathematics, Pairing Function

Cf. A000027, A001511, A033879, A033880, A286449, A286260, A286451, A286460, A286592, A286593.

(define (A286595 n) (* (/ 1 2) (+ (expt (+ (A001511 n) (A286449 n)) 2) (- (A001511 n)) (- (* 3 (A286449 n))) 2)))

a(n) = (1/2)*(2 + ((A001511(n)+A286449(n))^2) - A001511(n) - 3*A286449(n)).

A318449 Numerators of the sequence whose Dirichlet convolution with itself yields A001511, the 2-adic valuation of 2n.

Original entry on oeis.org

1, 1, 1, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 1, 1, 3, 1, 5, 1, 1, 1, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 1, 1, 1, 1, 3, 1, 1, 1, 3, 3, 1, 1, 1, 5, 1, 1, 1, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 1, 1, 1, 1, 3, 1, 1, 3, 1, 1, 1, 1, 1, 35, 1, 1, 1, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 1, 1, 1, 3, 3, 3, 1, 1, 1, 1, 1

Offset: 1

Antti Karttunen and Andrew Howroyd, Aug 29 2018

Antti Karttunen, Table of n, a(n) for n = 1..65537

Cf. A001511, A318450 (denominators).

a1511[n_] := IntegerExponent[2n, 2];
f[1] = 1; f[n_] := f[n] = 1/2 (a1511[n] - Sum[f[d] f[n/d], {d, Divisors[ n][[2 ;; -2]]}]);
Table[f[n] // Numerator, {n, 1, 105}] (* Jean-François Alcover, Sep 13 2018 *)

up_to = 65537;
A001511(n) = 1+valuation(n,2);
DirSqrt(v) = {my(n=#v, u=vector(n)); u[1]=1; for(n=2, n, u[n]=(v[n]/v[1] - sumdiv(n, d, if(d>1&&dA317937.
v318449_51 = DirSqrt(vector(up_to, n, A001511(n)));
A318449(n) = numerator(v318449_51[n]);

a(n) = numerator of f(n), where f(1) = 1, f(n) = (1/2) * (A001511(n) - Sum_{d|n, d>1, d 1.

Sum_{k=1..n} A318449(k) / A318450(k) ~ n * sqrt(2/(Pi*log(n))) * (1 + (1 - gamma/2 + log(2)/2)/(2*log(n))), where gamma is the Euler-Mascheroni constant A001620. - Vaclav Kotesovec, May 10 2025

A324817 a(n) = sign(A323244(n))*A001511(A323244(n)), with a(n) = 0 if A323244(n) = 0.

Original entry on oeis.org

0, 1, 1, 2, 1, 3, 1, 2, 0, 1, 1, 2, 1, 5, 2, 2, 1, 3, 1, 2, -1, 2, 1, 2, -3, 2, 3, 2, 1, 2, 1, 2, 2, 2, -2, 2, 1, 9, -3, 2, 1, 3, 1, 2, 4, 2, 1, 2, -3, 1, 4, 2, 1, 3, -1, 2, -3, 3, 1, 2, 1, 2, 5, 2, 2, 2, 1, 2, 2, 4, 1, 2, 1, 2, 2, 2, -2, 2, 1, 2, -3, 2, 1, 2, -4, 2, -3, 2, 1, 3, -1, 2, 2, 2, -3, 2, 1, 1, -3, 2, 1, 3, 1, 2, -3

Offset: 1

Antti Karttunen, Mar 17 2019

sign

Antti Karttunen, Table of n, a(n) for n = 1..10000 (based on Hans Havermann's factorization of A156552)
Index entries for sequences related to binary expansion of n
Index entries for sequences computed from indices in prime factorization
Index entries for sequences related to sigma(n)

Cf. A001511, A156552, A323243, A323244, A324724, A324725, A324731, A324732.

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 by David A. Corneth
A323244(n) = ((2*A156552(n))-A323243(n)); \\ Needs also code from A323243.
A001511ext(n) = if(!n,n,sign(n)*(1+valuation(n,2))); \\ Like A001511 but gives 0 for 0 and -A001511(-n) for negative numbers.
A324817(n) = A001511ext(A323244(n));

If A323244(n) = 0, then a(n) = 0, otherwise a(n) = sign(A323244(n)) * A001511(A323244(n)).

a(p) = 1 for all primes p.

cp's OEIS Frontend

A183036 G.f.: exp( Sum_{n>=1} A001511(n)*2^A001511(n)*x^n/n ) where A001511(n) equals the 2-adic valuation of 2n.

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A183037 a(n) = A001511(n)*2^A001511(n) where A001511(n) equals the 2-adic valuation of 2n.

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A217553 G.f.: exp( Sum_{n>=1} 4^A001511(n) * x^n/n ), where 2^A001511(n) is the highest power of 2 that divides 2*n.

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A253790 a(1) = 1; thereafter, odd numbers such that A055396(n) = A001511(n-1).

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A286367 Compound filter: a(n) = P(A001511(n), A286364(n)), where P(n,k) is sequence A000027 used as a pairing function.

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A286451 Compound filter (2-adic valuation of sigma(n) & 2-adic valuation of n): a(n) = P(A286357(n), A001511(n)), where P(n,k) is sequence A000027 used as a pairing function, with a(1) = 0 by an explicit convention.

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A286461 Compound filter (2-adic valuation of n & 4k+1,4k+3 prime-signature combination of 2n-1): a(n) = P(A001511(n), A286364((2*n)-1)), where P(n,k) is sequence A000027 used as a pairing function.

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A286595 Compound filter (2-adic valuation & deficiency/abundance): a(n) = P(A001511(n), A286449(n)), where P(n,k) is sequence A000027 used as a pairing function.

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A183036 G.f.: exp( Sum_{n>=1} A001511(n)2^A001511(n)x^n/n ) where A001511(n) equals the 2-adic valuation of 2n.