A229062 -id:A229062 - cp's OEIS frontend

A286368 a(n) = 4A072401(n) + 2A229062(n) + A010052(n).

3, 2, 0, 3, 2, 0, 4, 2, 3, 2, 0, 0, 2, 0, 4, 3, 2, 2, 0, 2, 0, 0, 4, 0, 3, 2, 0, 4, 2, 0, 4, 2, 0, 2, 0, 3, 2, 0, 4, 2, 2, 0, 0, 0, 2, 0, 4, 0, 3, 2, 0, 2, 2, 0, 4, 0, 0, 2, 0, 4, 2, 0, 4, 3, 2, 0, 0, 2, 0, 0, 4, 2, 2, 2, 0, 0, 0, 0, 4, 2, 3, 2, 0, 0, 2, 0, 4, 0, 2, 2, 0, 4, 0, 0, 4, 0, 2, 2, 0, 3, 2, 0, 4, 2, 0, 2, 0, 0, 2, 0, 4, 4, 2, 0, 0, 2, 2, 0, 4, 0

Offset: 1

Antti Karttunen, May 08 2017

nonn

Partitions natural numbers to the same equivalence classes as A002828. That is, for all i, j: a(i) = a(j) <=> A002828(i) = A002828(j). To get A002828 replace 0's with 3's, 3's with 1's and keep 2's as 2's and 4's as 4's.

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

Cf. A002828, A010052, A072401, A229062, A286366.

(define (A286368 n) (+ (* 4 (A072401 n)) (* 2 (A229062 n)) (A010052 n)))

a(n) = 4*A072401(n) + 2*A229062(n) + A010052(n).

A002828 Least number of squares that add up to n.

Original entry on oeis.org

0, 1, 2, 3, 1, 2, 3, 4, 2, 1, 2, 3, 3, 2, 3, 4, 1, 2, 2, 3, 2, 3, 3, 4, 3, 1, 2, 3, 4, 2, 3, 4, 2, 3, 2, 3, 1, 2, 3, 4, 2, 2, 3, 3, 3, 2, 3, 4, 3, 1, 2, 3, 2, 2, 3, 4, 3, 3, 2, 3, 4, 2, 3, 4, 1, 2, 3, 3, 2, 3, 3, 4, 2, 2, 2, 3, 3, 3, 3, 4, 2, 1, 2, 3, 3, 2, 3, 4, 3, 2, 2, 3, 4, 3, 3, 4, 3, 2, 2, 3, 1, 2, 3, 4, 2, 3

Offset: 0

N. J. A. Sloane

Lagrange's "Four Squares theorem" states that a(n) <= 4.
It is easy to show that this is also the least number of squares that add up to n^3.
a(n) is the number of iterations in f(...f(f(n))...) to reach 0, where f(n) = A262678(n) = n - A262689(n)^2. Allows computation of this sequence without Lagrange's theorem. - Antti Karttunen, Sep 09 2016
It is also easy to show that a(k^2*n) = a(n) for k > 0: Clearly a(k^2*n) <= a(n) but for all 4 cases of a(n) there is no k which would result in a(k^2*n) < a(n). - Peter Schorn, Sep 06 2021

N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Alois P. Heinz, Table of n, a(n) for n = 0..20000 (first 1001 terms from T. D. Noe with corrections from Michel Marcus)
F. Michel Dekking, Morphisms, Symbolic Sequences, and Their Standard Forms, Journal of Integer Sequences, Vol. 19 (2016), Article 16.1.1.
N. J. A. Sloane, Transforms.
Eric Weisstein's World of Mathematics, Square Number.

Cf. A000290, A000415, A000419, A002376, A004215, A000378, A001481.

Cf. A010052, A025426, A025427, A053610, A062535, A072401, A229062, A255131, A260728, A260731, A260734, A262678, A262689, A262690, A276573.

a002828 0 = 0  -- confessedly  /= 1, as sum [] == 0
a002828 n | a010052 n == 1 = 1
          | a025426 n > 0 = 2 | a025427 n > 0 = 3 | otherwise = 4
-- Reinhard Zumkeller, Feb 26 2015

with(transforms);
sq:=[seq(n^2, n=1..20)];
LAGRANGE(sq,4,120);
# alternative:
f:= proc(n) local F,x;
   if issqr(n) then return 1 fi;
   if nops(select(t -> t[1] mod 4 = 3 and t[2]::odd, ifactors(n)[2])) = 0 then return 2 fi;
   x:= n/4^floor(padic:-ordp(n,2)/2);
   if x mod 8 = 7 then 4 else 3 fi
end proc:
0, seq(f(n),n=1..200); # Robert Israel, Jun 14 2016
# next Maple program:
b:= proc(n, i) option remember; convert(series(`if`(n=0, 1, `if`(i<1, 0,
      b(n, i-1)+(s-> `if`(s>n, 0, x*b(n-s, i)))(i^2))), x, 5), polynom)
    end:
a:= n-> ldegree(b(n, isqrt(n))):
seq(a(n), n=0..105);  # Alois P. Heinz, Oct 30 2021

SquareCnt[n_] := If[SquaresR[1, n] > 0, 1, If[SquaresR[2, n] > 0, 2, If[SquaresR[3, n] > 0, 3, 4]]]; Table[SquareCnt[n], {n, 150}] (* T. D. Noe, Apr 01 2011 *)
sc[n_]:=Module[{s=SquaresR[Range[4],n]},If[First[s]>0,1,Length[ First[ Split[ s]]]+1]]; Join[{0},Array[sc,110]] (* Harvey P. Dale, May 21 2014 *)

istwo(n:int)=my(f);if(n<3,return(n>=0););f=factor(n>>valuation(n, 2)); for(i=1,#f[,1],if(bitand(f[i,2],1)==1&&bitand(f[i,1],3)==3, return(0)));1
isthree(n:int)=my(tmp=valuation(n,2));bitand(tmp,1)||bitand(n>>tmp,7)!=7
a(n)=if(isthree(n), if(issquare(n), !!n, 3-istwo(n)), 4) \\ Charles R Greathouse IV, Jul 19 2011, revised Mar 17 2022

from sympy import factorint
def A002828(n):
    if n == 0: return 0
    f = factorint(n).items()
    if not any(e&1 for p,e in f): return 1
    if all(p&3<3 or e&1^1 for p,e in f): return 2
    return 3+(((m:=(~n&n-1).bit_length())&1^1)&int((n>>m)&7==7)) # Chai Wah Wu, Aug 01 2023

from sympy.core.power import isqrt
def A002828(n):
    dp = [-1] * (n + 1)
    dp[0] = 0
    for i in range(1, n + 1):
        S = []
        r = isqrt(i)
        for j in range(1, r + 1):
            S.append(1 + dp[i - (j**2)])
        dp[i] = min(S)
    return dp[-1] # Darío Clavijo, Apr 21 2025

;; The first one follows Charles R Greathouse IV's PARI-code above:
(define (A002828 n) (cond ((zero? n) n) ((= 1 (A010052 n)) 1) ((= 1 (A229062 n)) 2) (else (+ 3 (A072401 n)))))
(define (A229062 n) (- 1 (A000035 (A260728 n))))
;; We can also compute this without relying on Lagrange's theorem. The following recursion-formula should be used together with the second Scheme-implementation of A262689 given in the Program section that entry:
(definec (A002828 n) (if (zero? n) n (+ 1 (A002828 (- n (A000290 (A262689 n)))))))
;; Antti Karttunen, Sep 09 2016

From Antti Karttunen, Sep 09 2016: (Start)
a(0) = 0; and for n >= 1, if A010052(n) = 1 [when n is a square], a(n) = 1, otherwise, if A229062(n)=1, then a(n) = 2, otherwise a(n) = 3 + A072401(n). [After Charles R Greathouse IV's PARI program.]
a(0) = 0; for n >= 1, a(n) = 1 + a(n - A262689(n)^2), (see comments).
a(n) = A053610(n) - A062535(n).
(End)

More terms from Arlin Anderson (starship1(AT)gmail.com)

A077773 Number of integers between n^2 and (n+1)^2 that are the sum of two squares; multiple representations are counted once.

Original entry on oeis.org

0, 1, 2, 2, 3, 4, 4, 5, 6, 6, 7, 6, 9, 8, 8, 10, 10, 11, 11, 12, 11, 14, 12, 13, 15, 16, 15, 15, 17, 16, 17, 19, 18, 19, 20, 19, 20, 21, 20, 22, 22, 24, 22, 25, 23, 26, 26, 24, 29, 26, 27, 28, 27, 29, 26, 31, 32, 30, 29, 33, 33, 31, 31, 35, 34, 35, 35, 35, 36, 37, 37, 33, 42, 37, 38

Offset: 0

T. D. Noe, Nov 20 2002

nonn

Related to the circle problem, cf. A077770. See A077774 for a more restrictive case. A077768 counts the representations multiply.
Number of integers k in range [n^2, ((n+1)^2)-1] for which 2 = the least number of squares that add up to k (A002828). Because of this interpretation a(0)=0 was prepended to the beginning. - Antti Karttunen, Oct 04 2016
This sequence is not surjective, since, for instance, there is no n such that a(n) = 46. This follows from a bound observed by Jon E. Schoenfield, that if a(n) = m then n < ((m+1)^2)/2, and the fact that a(n) != 46 for all n < 1105. - Rainer Rosenthal, Jul 25 2023

			a(8)=6 because 65=64+1=49+16, 68=64+4, 72=36+36, 73=64+9, 74=49+25 and 80=64+16 are between squares 64 and 81. Note that 65 is counted only once.

Hugo Pfoertner, Table of n, a(n) for n = 0..10000 (terms 0..1024 from T. D. Noe and Antti Karttunen).
Hugo Pfoertner, Table of n, a(n) for n = 0..500000
Rainer Rosenthal, Illustrating A077773

Cf. A000290, A000404, A002828, A010052, A077768, A077770, A077774, A229062, A277192, A277193, A277194.

Cf. A363762 (terms not occurring in this sequence), A363763.

maxN=100; lst={}; For[n=1, n<=maxN, n++, sqrs={}; i=n; j=0; While[i>=j, j=1; While[i^2+j^2<(n+1)^2, If[i>=j&&i^2+j^2>n^2, AppendTo[sqrs, i^2+j^2]]; j++ ]; i--; j-- ]; AppendTo[lst, Length[Union[sqrs]]]]; lst

a(N)=s=0;for(n=N^2+1,(N+1)^2-1,f=0;r=sqrtint(n);forstep(i=r,1,-1,if(issquare(n-i*i),f=1;s=s+1;break)));s /* Ralf Stephan, Sep 17 2013 */

from sympy import factorint
def A077773(n): return sum(1 for m in range(n**2+1,(n+1)**2) if all(p==2 or p&3==1 or e&1^1 for p, e in factorint(m).items())) # Chai Wah Wu, Jun 20 2023

(define (A077773 n) (add (lambda (i) (* (- 1 (A010052 i)) (A229062 i))) (A000290 n) (+ -1 (A000290 (+ 1 n)))))
;; Implements sum_{i=lowlim..uplim} intfun(i)
(define (add intfun lowlim uplim) (let sumloop ((i lowlim) (res 0)) (cond ((> i uplim) res) (else (sumloop (1+ i) (+ res (intfun i)))))))
;; Antti Karttunen, Oct 04 2016

a(n) = Sum_{i=n^2+1..(n+1)^2-1} A229062(i). - Ralf Stephan, Sep 17 2013
From Antti Karttunen, Oct 04 2016: (Start)
For n >= 0, a(n) + A277193(n) + A277194(n) = 2n.
For n >= 1, A277192(n) = a(n) + A277194(n). (End)

Term a(0)=0 prepended by Antti Karttunen, Oct 04 2016

A260728 Bitwise-OR of the exponents of all 4k+3 primes in the prime factorization of n.

Original entry on oeis.org

0, 0, 0, 1, 0, 0, 1, 1, 0, 2, 0, 1, 1, 0, 1, 1, 0, 0, 2, 1, 0, 1, 1, 1, 1, 0, 0, 3, 1, 0, 1, 1, 0, 1, 0, 1, 2, 0, 1, 1, 0, 0, 1, 1, 1, 2, 1, 1, 1, 2, 0, 1, 0, 0, 3, 1, 1, 1, 0, 1, 1, 0, 1, 3, 0, 0, 1, 1, 0, 1, 1, 1, 2, 0, 0, 1, 1, 1, 1, 1, 0, 4, 0, 1, 1, 0, 1, 1, 1, 0, 2, 1, 1, 1, 1, 1, 1, 0, 2, 3, 0, 0, 1, 1, 0, 1, 0, 1, 3, 0, 1, 1, 1, 0, 1, 1, 0, 2, 1, 1, 1

Offset: 0

Antti Karttunen, Aug 12 2015

nonn

A001481 (numbers that are the sum of 2 squares) gives the positions of even terms in this sequence, while its complement A022544 (numbers that are not the sum of 2 squares) gives the positions of odd terms.

If instead of bitwise-oring (A003986) we added in ordinary way the exponents of 4k+3 primes together, we would get the sequence A065339. For the positions where these two sequences differ see A260730.

			For n = 21 = 3^1 * 7^1 we compute A003986(1,1) = 1, thus a(21) = 1.
For n = 63 = 3^2 * 7^1 we compute A003986(2,1) = A003986(1,2) = 3, thus a(63) = 3.

Antti Karttunen, Table of n, a(n) for n = 0..10000

Cf. A000035, A001481, A022544, A003986, A020639, A028234, A032742, A067029, A097706, A229062, A260730.
Cf. also A267113, A267116, A267099.
Differs from A065339 for the first time at n=21, where a(21) = 1, while A065339(21)=2.

Table[BitOr @@ (Map[Last, FactorInteger@ n /. {p_, } /; MemberQ[{0, 1, 2}, Mod[p, 4]] -> Nothing]), {n, 0, 120}] (* _Michael De Vlieger, Feb 07 2016 *)

from functools import reduce
from operator import or_
from sympy import factorint
def A260728(n): return reduce(or_,(e for p, e in factorint(n).items() if p & 3 == 3),0) # Chai Wah Wu, Jun 28 2022

(define (A260728 n) (cond ((< n 3) 0) ((even? n) (A260728 (/ n 2))) ((= 1 (modulo (A020639 n) 4)) (A260728 (A032742 n))) (else (A003986bi (A067029 n) (A260728 (A028234 n)))))) ;; A003986bi implements bitwise-or (see A003986).

If n < 3, a(n) = 0; thereafter, for any even n: a(n) = a(n/2), for any n with its smallest prime factor (A020639) of the form 4k+1: a(n) = a(A032742(n)), otherwise [when A020639(n) is of the form 4k+3] a(n) = A003986(A067029(n),a(A028234(n))).
Other identities. For all n >= 0:
A229062(n) = 1 - A000035(a(n)). [Reduced modulo 2 and complemented, the sequence gives the characteristic function of A001481.]
a(n) = a(A097706(n)). [The result depends only on the prime factors of the form 4k+3.]
a(n) = A267116(A097706(n)).
a(n) = A267113(A267099(n)).

A277193 Number of integers k in range [n^2, ((n+1)^2)-1] for which 3 = the least number of squares that add up to k (A002828).

Original entry on oeis.org

0, 1, 1, 3, 4, 4, 6, 6, 8, 9, 9, 12, 11, 14, 15, 14, 17, 18, 19, 19, 23, 20, 24, 25, 25, 26, 29, 29, 30, 32, 32, 32, 36, 36, 37, 39, 41, 40, 42, 43, 45, 45, 47, 46, 50, 49, 50, 54, 52, 55, 56, 57, 60, 60, 63, 60, 62, 65, 68, 64, 67, 70, 72, 69, 73, 74, 75, 76, 78, 78, 80, 84, 79, 85, 84, 84, 88, 89, 90, 90, 91, 94, 94, 97, 94, 99

Offset: 0

Antti Karttunen, Oct 04 2016

nonn

Antti Karttunen, Table of n, a(n) for n = 0..512

Cf. A000290, A002828, A010052, A072401, A077773, A229062, A277194.

After the initial zero, one less than A277191.

(define (A277193 n) (add (lambda (i) (* (- 1 (A010052 i)) (- 1 (A229062 i)) (- 1 (A072401 i)))) (A000290 n) (+ -1 (A000290 (+ 1 n)))))
;; Implements sum_{i=lowlim..uplim} intfun(i)
(define (add intfun lowlim uplim) (let sumloop ((i lowlim) (res 0)) (cond ((> i uplim) res) (else (sumloop (1+ i) (+ res (intfun i)))))))

Sum_{i=n^2 .. ((n+1)^2)-1} (1-A010052(i))*(1-A229062(i))*(1-A072401(i)).
Other identities. For all n >= 0:
1 + A077773(n) + a(n) + A277194(n) = 2n+1.
For n >= 1, a(n) = A277191(n)-1.

A277194 Number of integers k in range [n^2, ((n+1)^2)-1] for which 4 = the least number of squares that add up to k (A002828).

Original entry on oeis.org

0, 0, 1, 1, 1, 2, 2, 3, 2, 3, 4, 4, 4, 4, 5, 6, 5, 5, 6, 7, 6, 8, 8, 8, 8, 8, 8, 10, 9, 10, 11, 11, 10, 11, 11, 12, 11, 13, 14, 13, 13, 13, 15, 15, 15, 15, 16, 16, 15, 17, 17, 17, 17, 17, 19, 19, 18, 19, 19, 21, 20, 21, 21, 22, 21, 21, 22, 23, 22, 23, 23, 25, 23, 24, 26, 25, 26, 26, 26, 27, 26, 27, 27, 28, 29, 28, 29, 30, 29, 30, 30, 31

Offset: 0

Antti Karttunen, Oct 04 2016

nonn

Antti Karttunen, Table of n, a(n) for n = 0..512

Cf. A000290, A002828, A010052, A072401, A077773, A229062, A277192, A277193.

(define (A277194 n) (add A072401 (A000290 n) (+ -1 (A000290 (+ 1 n)))))
;; Implements sum_{i=lowlim..uplim} intfun(i)
(define (add intfun lowlim uplim) (let sumloop ((i lowlim) (res 0)) (cond ((> i uplim) res) (else (sumloop (1+ i) (+ res (intfun i)))))))

a(n) = Sum_{i=n^2 .. ((n+1)^2)-1} A072401(i).
Other identities.
For n >= 0, 1 + A077773(n) + A277193(n) + a(n) = 2n+1.
For n >= 1, A277192(n) = A077773(n) + a(n).

A102548 Number of positive integers <= n that are expressible in the form u^2+v^2, with u and v integers.

Original entry on oeis.org

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

Offset: 1

Salvador Perez Gomez (pies314(AT)hotmail.com), Feb 24 2005

			a(8) = 5 because 1 = 0^2 + 1^2, 2 = 1^2 + 1^2, 4 = 0^2 + 2^2, 5 = 1^2 + 2^2, 8 = 2^2 + 2^2, but 3,6 and 7 are not of the form u^2 + v^2, with u and v integers.

David A. Corneth, Table of n, a(n) for n = 1..10000
Yoichi Motohashi, On the distribution of prime numbers which are of the form x^2+y^2+1, Acta Arith. 16 (1969/70), 351-363. MR0288086 (44 #5284). See Eq. (1.2).
D. Shanks, The second-order term in the asymptotic expansion of B(x), Mathematics of Computation 18 (1964), pp. 75-86.
Eric Weisstein's World of Mathematics, Landau-Ramanujan Constant.

Cf. A000161, A000691, A001481, A229062.

a := proc(n) local aux,i,m,u,v; aux:=0; for i from 1 to n do m:=floor(sqrt(i/2)); for u from 0 to m do v:=sqrt(i-u^2); if (v = floor(v)) then aux:=aux+1; u:=m; end if; end do; end do; aux; end proc:

a[1]=1; a[n_]:= a[n]= a[n-1] + If[SquaresR[2, n]>0, 1, 0]; Table[a[n], {n,75}] (* Jean-François Alcover, Mar 31 2015 *)

first(n)= my(v = vector(n + 1), res = vector(n)); res[1] = 1; for(i = 0, sqrtint(n), for(j = i, sqrtint(n - i^2), v[i^2+j^2+1] = 1 ) ); for(i = 2, #res, res[i] = res[i-1] + v[i+1]; ); res \\ David A. Corneth, Jun 05 2020

from itertools import count, accumulate, islice
from sympy import factorint
def A102548_gen(): # generator of terms
    return accumulate(int(all(p & 3 != 3 or e & 1 == 0 for p, e in factorint(n).items())) for n in count(1))
A102548_list = list(islice(A102548_gen(),30)) # Chai Wah Wu, Jun 28 2022

From David A. Corneth, Jun 05 2020: (Start)
A000161(a(n)) > 0.
a(n) = (partial sum of A229062 up to n) - 1. (End)
a(n) = n/sqrt(log n) * (K + B2/log n + O(1/log^2 n)), where K = A064533 and B2 = A227158. In particular, a(n) ~ Kn/sqrt(log n). - Charles R Greathouse IV, Dec 03 2022

Name clarified by David A. Corneth, Jun 05 2020

cp's OEIS Frontend

A286368 a(n) = 4*A072401(n) + 2*A229062(n) + A010052(n).

Views

Author

Keywords

Comments

Links

Crossrefs

Programs

Scheme

Formula

A002828 Least number of squares that add up to n.

Views

Author

Keywords

Comments

References

Links

Crossrefs

Programs

Haskell

Maple

Mathematica

PARI

Python

Python

Scheme

Formula

Extensions

A077773 Number of integers between n^2 and (n+1)^2 that are the sum of two squares; multiple representations are counted once.

Views

Author

Keywords

Comments

Examples

Links

Crossrefs

Programs

Mathematica

PARI

Python

Scheme

Formula

Extensions

A260728 Bitwise-OR of the exponents of all 4k+3 primes in the prime factorization of n.

Views

Author

Keywords

Comments

Examples

Links

Crossrefs

Programs

Mathematica

Python

Scheme

Formula

A277193 Number of integers k in range [n^2, ((n+1)^2)-1] for which 3 = the least number of squares that add up to k (A002828).

Views

Author

Keywords

Links

Crossrefs

Programs

Scheme

Formula

A277194 Number of integers k in range [n^2, ((n+1)^2)-1] for which 4 = the least number of squares that add up to k (A002828).

Views

Author

Keywords

Links

Crossrefs

Programs

Scheme

Formula

A102548 Number of positive integers <= n that are expressible in the form u^2+v^2, with u and v integers.

Views

Author

Keywords

Examples

A286368 a(n) = 4A072401(n) + 2A229062(n) + A010052(n).