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 11 results. Next

A038465 Sums of 3 distinct powers of 3.

Original entry on oeis.org

13, 31, 37, 39, 85, 91, 93, 109, 111, 117, 247, 253, 255, 271, 273, 279, 325, 327, 333, 351, 733, 739, 741, 757, 759, 765, 811, 813, 819, 837, 973, 975, 981, 999, 1053, 2191, 2197, 2199, 2215, 2217, 2223, 2269, 2271, 2277, 2295, 2431, 2433, 2439, 2457, 2511, 2917
Offset: 1

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Author

Keywords

Crossrefs

Base 3 interpretation of A038445.

Programs

  • Mathematica
    Total/@Subsets[3^Range[0,10],{3}]//Union (* Harvey P. Dale, Jul 10 2017 *)
  • Python
    from math import comb, isqrt
    from sympy import integer_nthroot
    def A038465(n): return 3**((r:=n-1-comb((m:=integer_nthroot(6*n,3)[0])+(t:=(n>comb(m+2,3)))+1,3))-comb((k:=isqrt(b:=r+1<<1))+(b>k*(k+1)),2))+3**((a:=isqrt(s:=n-comb(m-(t^1)+2,3)<<1))+((s<<2)>(a<<2)*(a+1)+1))+3**(m+t+1) # Chai Wah Wu, Apr 04 2025

Extensions

Offset corrected by Amiram Eldar, Jul 13 2022

A038466 Sums of 4 distinct powers of 3.

Original entry on oeis.org

40, 94, 112, 118, 120, 256, 274, 280, 282, 328, 334, 336, 352, 354, 360, 742, 760, 766, 768, 814, 820, 822, 838, 840, 846, 976, 982, 984, 1000, 1002, 1008, 1054, 1056, 1062, 1080, 2200, 2218, 2224, 2226, 2272, 2278, 2280, 2296, 2298, 2304, 2434, 2440, 2442, 2458
Offset: 1

Views

Author

Keywords

Crossrefs

Base 3 interpretation of A038446.

Programs

  • Mathematica
    Sort[Plus @@@ Subsets[3^Range[0, 7], {4}]] (* Amiram Eldar, Jul 13 2022 *)
  • Python
    from itertools import islice
    def A038466_gen(): # generator of terms
        yield int(bin(n:=15)[2:],3)
        while True: yield int(bin((n:=n^((a:=-n&n+1)|(a>>1)) if n&1 else ((n&~(b:=n+(a:=n&-n)))>>a.bit_length())^b))[2:],3)
    A038466_list = list(islice(A038466_gen(),30)) # Chai Wah Wu, Apr 04 2025

Extensions

Offset corrected by Amiram Eldar, Jul 13 2022

A038467 Sums of 5 distinct powers of 3.

Original entry on oeis.org

121, 283, 337, 355, 361, 363, 769, 823, 841, 847, 849, 985, 1003, 1009, 1011, 1057, 1063, 1065, 1081, 1083, 1089, 2227, 2281, 2299, 2305, 2307, 2443, 2461, 2467, 2469, 2515, 2521, 2523, 2539, 2541, 2547, 2929, 2947, 2953, 2955, 3001, 3007, 3009, 3025, 3027, 3033
Offset: 1

Views

Author

Keywords

Crossrefs

Base 3 interpretation of A038447.

Programs

  • Mathematica
    Union[Total/@Subsets[3^Range[0,7],{5}]]  (* Harvey P. Dale, Feb 23 2011 *)

A038468 Sums of 6 distinct powers of 3.

Original entry on oeis.org

364, 850, 1012, 1066, 1084, 1090, 1092, 2308, 2470, 2524, 2542, 2548, 2550, 2956, 3010, 3028, 3034, 3036, 3172, 3190, 3196, 3198, 3244, 3250, 3252, 3268, 3270, 3276, 6682, 6844, 6898, 6916, 6922, 6924, 7330, 7384, 7402, 7408, 7410, 7546, 7564, 7570, 7572, 7618
Offset: 1

Views

Author

Keywords

Crossrefs

Base 3 interpretation of A038448.

Programs

  • Mathematica
    Sort[Plus @@@ Subsets[3^Range[0, 8], {6}]] (* Amiram Eldar, Jul 12 2022 *)
  • Python
    from itertools import islice
    def A038468_gen(): # generator of terms
        yield int(bin(n:=63)[2:],3)
        while True: yield int(bin((n:=n^((a:=-n&n+1)|(a>>1)) if n&1 else ((n&~(b:=n+(a:=n&-n)))>>a.bit_length())^b))[2:],3)
    A038468_list = list(islice(A038468_gen(),30)) # Chai Wah Wu, Apr 05 2025

Extensions

Offset corrected by Amiram Eldar, Jul 12 2022

A038469 Sums of 7 distinct powers of 3.

Original entry on oeis.org

1093, 2551, 3037, 3199, 3253, 3271, 3277, 3279, 6925, 7411, 7573, 7627, 7645, 7651, 7653, 8869, 9031, 9085, 9103, 9109, 9111, 9517, 9571, 9589, 9595, 9597, 9733, 9751, 9757, 9759, 9805, 9811, 9813, 9829, 9831, 9837, 20047, 20533, 20695, 20749, 20767, 20773, 20775
Offset: 1

Views

Author

Keywords

Crossrefs

Base 3 interpretation of A038449.

Programs

  • Mathematica
    Sort[Plus @@@ Subsets[3^Range[0, 8], {7}]] (* Amiram Eldar, Jul 13 2022 *)

Extensions

Offset corrected by Amiram Eldar, Jul 13 2022

A309758 Numbers that are sums of consecutive powers of 3.

Original entry on oeis.org

1, 3, 4, 9, 12, 13, 27, 36, 39, 40, 81, 108, 117, 120, 121, 243, 324, 351, 360, 363, 364, 729, 972, 1053, 1080, 1089, 1092, 1093, 2187, 2916, 3159, 3240, 3267, 3276, 3279, 3280, 6561, 8748, 9477, 9720, 9801, 9828, 9837, 9840, 9841, 19683, 26244, 28431
Offset: 1

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Author

Ilya Gutkovskiy, Aug 15 2019

Keywords

Comments

Numbers of the form (3^i - 3^j)/2 with i > j.

Examples

			1080 = 3^3 + 3^4 + 3^5 + 3^6, so 1080 is in the sequence.
+------+--------+
| a(n) | base 3*|
+------+--------+
|   1  |     1  |
|   3  |    10  |
|   4  |    11  |
|   9  |   100  |
|  12  |   110  |
|  13  |   111  |
|  27  |  1000  |
|  36  |  1100  |
|  39  |  1110  |
|  40  |  1111  |
+------+--------+
* - a(n) written in base 3.
		

Crossrefs

Programs

  • Maple
    [seq(seq((3^i-3^j)/2,j=i-1..0,-1),i=1..20)]; # Robert Israel, Aug 19 2019
  • Python
    from math import isqrt
    def A309758(n): return 3**(m:=isqrt(n<<3)+1>>1)-3**(m*(m+1)-(n<<1)>>1)>>1 # Chai Wah Wu, Apr 04 2025

A371709 Expansion of g.f. A(x) satisfying A( x*A(x)^2 + x*A(x)^3 ) = A(x)^3.

Original entry on oeis.org

1, 1, 1, 2, 6, 16, 39, 99, 271, 764, 2157, 6128, 17658, 51534, 151635, 448962, 1337493, 4008040, 12072594, 36524898, 110943633, 338218626, 1034509917, 3173811240, 9763898994, 30113782641, 93094164244, 288415278638, 895332445053, 2784580242557, 8675408291598, 27072326322939
Offset: 1

Views

Author

Paul D. Hanna, May 02 2024

Keywords

Comments

Compare to the following identities of the Catalan function C(x) = x + C(x)^2 (A000108):
(1) C(x)^2 = C( x*C(x)*(1 + C(x)) ),
(2) C(x)^4 = C( x*C(x)^3*(1 + C(x))*(1 + C(x)^2) ),
(3) C(x)^8 = C( x*C(x)^7*(1 + C(x))*(1 + C(x)^2)*(1 + C(x)^4) ),
(4) C(x)^(2^n) = C( x*C(x)^(2^n-1)*Product_{k=0..n-1} (1 + C(x)^(2^k)) ) for n > 0.
a(3^n) == 1 (mod 3) for n >= 0.
a(2*3^n) == 1 (mod 3) for n >= 0.
a(n) == 2 (mod 3) iff n is the sum of 2 distinct powers of 3 (A038464).

Examples

			G.f. A(x) = x + x^2 + x^3 + 2*x^4 + 6*x^5 + 16*x^6 + 39*x^7 + 99*x^8 + 271*x^9 + 764*x^10 + 2157*x^11 + 6128*x^12 + 17658*x^13 + 51534*x^14 + 151635*x^15 + 448962*x^16 + ...
where A( x*A(x)^2*(1 + A(x)) ) = A(x)^3.
RELATED SERIES.
A(x)^2 = x^2 + 2*x^3 + 3*x^4 + 6*x^5 + 17*x^6 + 48*x^7 + 126*x^8 + 332*x^9 + 918*x^10 + 2616*x^11 + 7504*x^12 + ...
A(x)^3 = x^3 + 3*x^4 + 6*x^5 + 13*x^6 + 36*x^7 + 105*x^8 + 292*x^9 + 801*x^10 + 2256*x^11 + 6515*x^12 + 18981*x^13 + ...
A(x)^2 + A(x)^3 = x^2 + 3*x^3 + 6*x^4 + 12*x^5 + 30*x^6 + 84*x^7 + 231*x^8 + 624*x^9 + 1719*x^10 + 4872*x^11 + 14019*x^12 + 40599*x^13 + ...
Let B(x) be the series reversion of g.f. A(x), B(A(x)) = x, then
B(x) * (1+x)/(1+x^3) = x - 2*x^4 + 3*x^7 - 5*x^10 + 7*x^13 - 9*x^16 + 12*x^19 - 15*x^22 + 18*x^25 - 23*x^28 + ... + (-1)^n*A005704(n)*x^(3*n+1) + ...
where A005704 is the number of partitions of 3*n into powers of 3.
We can show that g.f. A(x) = A( x*A(x)^2*(1 + A(x)) )^(1/3) satisfies
(4) A(x) = x * Product_{n>=0} (1 + A(x)^(3^n))
by substituting x*A(x)^2*(1 + A(x)) for x in (4) to obtain
A(x)^3 = x * A(x)^2*(1 + A(x)) * Product_{n>=1} (1 + A(x)^(3^n))
which is equivalent to formula (4).
SPECIFIC VALUES.
A(3/10) = 0.526165645044542830201162330432965674027415264612114520...
A(1/4) = 0.353259384374080248921564026412797625837830114153200664...
A(1/5) = 0.255218141344695821239609680309162895225297482063273545...
A(t) = 1/2 and A(t*3/8) = 1/8 at t = (1/2)/Product_{n>=0} (1 + 1/2^(3^n)) = 0.295718718466711580562679377308518930409875701753934072...
A(t) = 1/3 and A(t*4/27) = 1/27 at t = (1/3)/Product_{n>=0} (1 + 1/3^(3^n)) = 0.241059181496179959557718992589733756750585121455883861...
A(t) = 1/4 and A(t*5/64) = 1/64 at t = (1/4)/Product_{n>=0} (1 + 1/4^(3^n)) = 0.196922325724019432212969925740117827612003158137366017...
		

Crossrefs

Programs

  • PARI
    /* Using series reversion of x/Product_{n>=0} (1 + x^(3^n)) */
    {a(n) = my(A); A = serreverse( x/prod(k=0,ceil(log(n)/log(3)), (1 + x^(3^k) +x*O(x^n)) ) ); polcoeff(A,n)}
    for(n=1,35, print1(a(n),", "))
    
  • PARI
    /* Using A(x)^3 = A( x*A(x)^2 + x*A(x)^3 ) */
    {a(n) = my(A=[1],F); for(i=1,n, A = concat(A,0); F = x*Ser(A);
    A[#A] = polcoeff( subst(F,x, x*F^2 + x*F^3 ) - F^3, #A+2) ); A[n]}
    for(n=1,35, print1(a(n),", "))

Formula

G.f. A(x) = Sum_{n>=1} a(n)*x^n satisfies the following formulas.
(1) A(x)^3 = A( x*A(x)^2*(1 + A(x)) ).
(2) A(x)^9 = A( x*A(x)^8*(1 + A(x))*(1 + A(x)^3) ).
(3) A(x)^27 = A( x*A(x)^26*(1 + A(x))*(1 + A(x)^3)*(1 + A(x)^9) ).
(4) A(x) = x * Product_{n>=0} (1 + A(x)^(3^n)).
(5) A(x) = Series_Reversion( x / Product_{n>=0} (1 + x^(3^n)) ).
a(n) ~ c * d^n / n^(3/2), where d = 3.2753449994351908157330968510747739... and c = 0.1559869008021616116037651076359... - Vaclav Kotesovec, May 03 2024
The radius of convergence r of g.f. A(x) and A(r) satisfy 1 = Sum_{n>=0} 3^n * A(r)^(3^n) / (1 + A(r)^(3^n)) and r = A(r) / Product_{n>=0} (1 + A(r)^(3^n)), where r = 0.30531134893345362211... = 1/d (d is given above) and A(r) = 0.600582105427215700175254768411726892599... - Paul D. Hanna, May 03 2024

A376226 G.f. satisfies A(x) = A(x^3 + 6*x*A(x)^3) / A(x^2 + 4*x*A(x)^2).

Original entry on oeis.org

1, 2, 10, 66, 518, 4484, 41424, 399900, 3983698, 40622502, 421780380, 4442833776, 47353725678, 509717438804, 5532808254500, 60492412303032, 665570138005230, 7363717939202660, 81872879608989990, 914314572022052508, 10251126194392776384, 115346231108018654736, 1302114832694059544892
Offset: 1

Views

Author

Paul D. Hanna, Oct 04 2024

Keywords

Comments

Compare to C(x) = C(x^3 + 3*x*C(x)^3) / C(x^2 + 2*x*C(x)^2), where C(x) = x + C(x)^2 is the g.f. of the Catalan numbers (A000108).
Conjectures:
(C1) a(n) == 1 (mod 3) iff n = 3^k for some k >= 0.
(C2) a(n) == 2 (mod 3) iff n = A038464(k)/2 for some k >= 1, where A038464 lists the sums of 2 distinct powers of 3.

Examples

			G.f.: A(x) = x + 2*x^2 + 10*x^3 + 66*x^4 + 518*x^5 + 4484*x^6 + 41424*x^7 + 399900*x^8 + 3983698*x^9 + 40622502*x^10 + 421780380*x^11 + 4442833776*x^12 + ...
where A(x) = A(x^3 + 6*x*A(x)^3) / A(x^2 + 4*x*A(x)^2).
RELATED SERIES.
A(x^2 + 4*x*A(x)^2) = x^2 + 4*x^3 + 18*x^4 + 112*x^5 + 794*x^6 + 6360*x^7 + 55266*x^8 + 509968*x^9 + 4914150*x^10 + 48889752*x^11 + 498234420*x^12 + ...
A(x^3 + 6*x*A(x)^3) = x^3 + 6*x^4 + 36*x^5 + 254*x^6 + 1980*x^7 + 16812*x^8 + 152002*x^9 + 1440828*x^10 + 14148936*x^11 + 142715046*x^12 + ...
A(x)^2 = x^2 + 4*x^3 + 24*x^4 + 172*x^5 + 1400*x^6 + 12360*x^7 + 115500*x^8 + 1123552*x^9 + 11255688*x^10 + 115291188*x^11 + 1201533048*x^12 + ...
A(x)^3 = x^3 + 6*x^4 + 42*x^5 + 326*x^6 + 2766*x^7 + 25020*x^8 + 237364*x^9 + 2332860*x^10 + 23547474*x^11 + 242620986*x^12 + ...
A(x)^2 / A(x^2 + 4*x*A(x)^2) = 1 + 6*x^2 + 36*x^3 + 354*x^4 + 3264*x^5 + 32010*x^6 + 320400*x^7 + 3276558*x^8 + 34050444*x^9 + 358651116*x^10 + 3820385664*x^11 + 41087069040*x^12 + ...
which also equals A(x)^3 / A(x^3 + 6*x*A(x)^3).
		

Programs

  • PARI
    {a(n) = my(A=[0,1],Ax=x); for(i=1,n, A=concat(A,0); Ax=Ser(A);
    A[#A] = polcoeff( subst(Ax,x, x^3 + 6*x*Ax^3 ) - Ax*subst(Ax,x, x^2 + 4*x*Ax^2 ),#A+1)); A[n+1]}
    for(n=1,25,print1(a(n),", "))

Formula

a(n) ~ c * d^n / n^(3/2), where d = 12.086418637032871629430806055580752... and c = 0.01774947449130389477598279659776... - Vaclav Kotesovec, Oct 10 2024

A384830 G.f. satisfies A(x) = A(x^3 - 3*x*A(x)^3) / A(x^2 - 2*x*A(x)^2).

Original entry on oeis.org

1, -1, 4, -21, 110, -616, 3738, -23619, 152470, -1003776, 6726702, -45720504, 314307018, -2181641134, 15269811260, -107651952999, 763745165826, -5448656285938, 39063995033178, -281309141648214, 2033846965665156, -14757571862304042, 107431429198117338, -784411267743868602, 5743068864740600214
Offset: 1

Views

Author

Paul D. Hanna, Jul 11 2025

Keywords

Comments

Compare to C(x) = C(x^3 + 3*x*C(x)^3) / C(x^2 + 2*x*C(x)^2), where C(x) = x + C(x)^2 is the g.f. of the Catalan numbers (A000108).
Conjectures:
(C.1) a(n) is odd iff n = 2^k for k >= 0.
(C.2) a(n) == 1 (mod 3) iff n = 3^k for k >= 0.
(C.3) a(n) == 2 (mod 3) iff n = A038464(k)/2 for k >= 1, where A038464 lists sums of 2 distinct powers of 3.

Examples

			G.f.: A(x)  = x - x^2 + 4*x^3 - 21*x^4 + 110*x^5 - 616*x^6 + 3738*x^7 - 23619*x^8 + 152470*x^9 - 1003776*x^10 + 6726702*x^11 - 45720504*x^12 + 314307018*x^13 - 2181641134*x^14 + 15269811260*x^15 - 107651952999*x^16 +- ...
where A(x) = A(x^3 - 3*x*A(x)^3) / A(x^2 - 2*x*A(x)^2).
RELATED SERIES.
A(x)^2 = x^2 - 2*x^3 + 9*x^4 - 50*x^5 + 278*x^6 - 1620*x^7 + 10029*x^8 - 64262*x^9 + 420054*x^10 - 2793960*x^11 + 18874530*x^12 + ...
A(x)^3 = x^3 - 3*x^4 + 15*x^5 - 88*x^6 + 516*x^7 - 3123*x^8 + 19771*x^9 - 128748*x^10 + 853182*x^11 - 5739306*x^12 + ...
A(x^3 - 3*x*A(x)^3) = x^3 - 3*x^4 + 9*x^5 - 46*x^6 + 270*x^7 - 1575*x^8 + 9517*x^9 - 60228*x^10 + 391950*x^11 - 2595666*x^12 + ...
A(x^2 - 2*x*A(x)^2) = x^2 - 2*x^3 + 3*x^4 - 14*x^5 + 92*x^6 - 528*x^7 + 3027*x^8 - 18674*x^9 + 120414*x^10 - 790332*x^11 + 5264400*x^12 + ...
A(x)^2 / A(x^2 - 2*x*A(x)^2) = 1 + 6*x^2 - 24*x^3 + 120*x^4 - 696*x^5 + 4362*x^6 - 27720*x^7 + 179496*x^8 - 1188324*x^9 + 8004222*x^10 - 54609300*x^11 + 376571358*x^12 + ...
which also equals A(x)^3 / A(x^3 - 3*x*A(x)^3).
SPECIFIC VALUES.
A(t) = 1/9 at t = 0.121516943263807312205895948801335726496880098390997...
A(t) = 1/10 at t = 0.10853522544585482043493483988448061537900985360239...
  where 1/10 = A(t^3 - 3*t/10^3) / A(t^2 - 2*t/10^2).
A(1/8) = 0.11406786932603073004140288621992624859772243547241...
  where A(1/8) = A(1/8^3 - 3/8*A(1/8)^3) / A(1/8^2 - 2/8*A(1/8)^2).
A(1/9) = 0.10221632839303036250437950418981106643715860663579...
A(1/10) = 0.09261382926552257152263444179118404183078004746053...
A(1/11) = 0.08467305103076088485212166668503171895257965884840...
A(1/12) = 0.07799525781645435314575205510854905593664831977089...
A(-1/8) = -0.1721552141574965794714379396217931153561352397408...
A(-1/9) = -0.1381403570271418152616530595087372513703838778026...
A(-1/10) = -0.1188984739221037989978618004289786780166116550840...
		

Crossrefs

Programs

  • PARI
    {a(n) = my(A=[0, 1], Ax=x); for(i=1, n, A=concat(A, 0); Ax=Ser(A);
    A[#A] = polcoeff( subst(Ax, x, x^3 - 3*x*Ax^3 ) - Ax*subst(Ax, x, x^2 - 2*x*Ax^2 ), #A+1)); A[n+1]}
    for(n=1, 25, print1(a(n), ", "))

Formula

a(n) ~ (-1)^(n+1) * c * d^n / n^(3/2), where d = 7.79529565596481925683030276174290122793451926009119... and c = 0.0350717712305315691918705178165312896756485548321... - Vaclav Kotesovec, Jul 16 2025

A385912 A diagonal (unsigned) of triangle A385910; a(n) = -A385910(n+2,n) for n >= 1.

Original entry on oeis.org

1, 8, 49, 296, 1815, 11284, 70924, 449616, 2869779, 18418400, 118749345, 768537120, 4990021764, 32489701776, 212048505160, 1386886206112, 9087724409547, 59646983740680, 392071446052195, 2580601721867400, 17005938279649935, 112190574812699460, 740878216459158960, 4897062582469861440, 32395964187696107700
Offset: 1

Views

Author

Paul D. Hanna, Jul 14 2025

Keywords

Comments

Triangle A385910 has g.f. A(x,y) where A(x,y) = A(x^3 + 3*x*y*A(x,y)^3, y) / A(x^2 + 2*x*y*A(x,y)^2, y).
The main diagonal of A385910 has g.f. G(x) = 1 + x*G(x)^3 (A001764).
Conjectures:
(C.1) a(n) is odd iff n = 2*A003714(k) + 1 for k >= 0, where A003714 is the Fibbinary numbers.
(C.2) a(n) == 1 (mod 3) iff n = 3^k + 1 for k >= 0.
(C.3) a(n) == 2 (mod 3) iff n = A038464(k)/2 + 1 for k >= 1 or n = 1, where A038464 lists sums of 2 distinct powers of 3.

Examples

			G.f. A(x) = x + 8*x^2 + 49*x^3 + 296*x^4 + 1815*x^5 + 11284*x^6 + 70924*x^7 + 449616*x^8 + 2869779*x^9 + 18418400*x^10 + 118749345*x^11 + 768537120*x^12 + ...
		

Crossrefs

Programs

  • PARI
    \\ a(n) = -A385910(n+2,n) for n >= 1
    {A385910(n) = my(A=[0, 1], Ax=x); for(i=1, n, A=concat(A, 0); Ax=Ser(A);
    A[#A] = polcoeff( subst(Ax, x, x^3 + 3*y*x*Ax^3 ) - Ax*subst(Ax, x, x^2 + 2*y*x*Ax^2 ), #A+1)); A[n+1]}
    for(n=1, 25, print1(polcoef(-A385910(n+2),n),", "))
Showing 1-10 of 11 results. Next