A007924 -id:A007924 - cp's OEIS frontend

A200947 Sequence A007924 expressed in decimal.

0, 1, 2, 4, 5, 8, 9, 16, 17, 18, 20, 32, 33, 64, 65, 66, 68, 128, 129, 256, 257, 258, 260, 512, 513, 514, 516, 517, 520, 1024, 1025, 2048, 2049, 2050, 2052, 2053, 2056, 4096, 4097, 4098, 4100, 8192, 8193, 16384, 16385, 16386, 16388, 32768, 32769, 32770

Offset: 0

Frank M Jackson, Nov 24 2011

nonn

			8=7+1, hence A007924(8)=10001, so a(8)=17.

Alois P. Heinz, Table of n, a(n) for n = 0..10000
Wikipedia, "Complete" sequence. [Wikipedia calls a sequence "complete" (sic) if every positive integer is a sum of distinct terms. This name is extremely misleading and should be avoided. - _N. J. A. Sloane_, May 20 2023]

Cf. A003714, A007895, A007924, A027941, A066352, A121559, A345297.

a:= proc(n) option remember; local m, p, r; m:=n; r:=0;
      while m>0 do
        if m=1 then r:=r+1; break fi;
        p:= prevprime(m+1); m:= m-p;
        r:= r+2^numtheory[pi](p)
      od; r
    end:
seq(a(n), n=0..52);  # Alois P. Heinz, Jun 12 2023

cprime[n_Integer] := If[n==0, 1, Prime[n]]; gentable[n_Integer] := (m=n; ptable={}; While[m != 0, (i = 0; While[cprime[i] <= m, i++]; j=0; While[j

a(n) = decimal(A007924(n)).

a(n) mod 2 = A121559(n) for n>=1. - Alois P. Heinz, Jun 12 2023

Edited by N. J. A. Sloane, May 20 2023

A066352 Pillai sequence: a(n) is the smallest term in A007924 requiring n primes.

Original entry on oeis.org

0, 1, 4, 27, 1354, 401429925999155061

Offset: 0

Copied from www.primepuzzles.net by Frank Ellermann, Dec 19 2001

a(5) computed independently in 2007 by R. J. Mathar and Luca & Thangadurai, both using Thomas Nicely's tables.
On Cramer's conjecture, the number of primes required is O(log* n), where log* is the iterated logarithm, so the rate of growth of a(n) is tetrational in n. - Charles R Greathouse IV, Aug 28 2010
The next term likely has hundreds of millions of digits. - Charles R Greathouse IV, Jun 29 2015

			The greatest prime <= 27 is 23; the greatest prime <= 27-23 is 3; 27-23-3 = 1, so the Pillai representation of 27 is 23+3+1, which uses more terms than all preceding numbers.

S. S. Pillai, "An arithmetical function concerning primes", Annamalai University Journal (1930), pp. 159-167.

Florian Luca and Ravindranathan Thangadurai, On an arithmetic function considered by Pillai, Journal de théorie des nombres de Bordeaux 21:3 (2009), pp. 695-701.
M. T. Marcos, Smarandache Prime Base representation, prime puzzle 141.
Thomas R. Nicely, First occurrence prime gaps [For local copy see A000101]
S. S. Pillai, On an Arithmetic Function concerning Primes, Journal Of The Annamalai University, Vol-1 (1932), pp. 159-167 (pages 204-212 in pdf).

Cf. A007924.

A072491(n)=if(n<4,n>0,1+A072491(n-precprime(n)))
print1(r=0);for(n=1,1e7,if(A072491(n)>r,r=a(n);print1(", "n)))
\\ Charles R Greathouse IV, Feb 04 2013

a(n) = 2*p(m) - p(m-1) with minimal m = pi(a(n)) so that p(m) = a(n-1) + p(m-1), where p(n) is A008578(n).

Edited by Charles R Greathouse IV, Oct 28 2009

Entry rewritten by Charles R Greathouse IV, Aug 28 2010

A007923 Lengths increase by 1, digits cycle through positive digits.

Original entry on oeis.org

1, 23, 456, 7891, 23456, 789123, 4567891, 23456789, 123456789, 1234567891, 23456789123, 456789123456, 7891234567891, 23456789123456, 789123456789123, 4567891234567891, 23456789123456789, 123456789123456789

Offset: 1

R. Muller

C. Ashbacher, Some Problems Concerning the Smarandache Deconstructive Sequence, J. Recreational Mathematics, Vol. 29, No. 2, pages 82-84.
K. Atanassov, On the 4th Smarandache Problem, Notes on Number Theory and Discrete Mathematics, Sophia, Bulgaria, Vol. 5 (1999), No. 1, 33-35.

John Cerkan, Table of n, a(n) for n = 1..994
K. Atanassov, On Some of Smarandache's Problems
F. Smarandache, Only Problems, Not Solutions!
Eric Weisstein's World of Mathematics, Smarandache Sequences

Cf. A001369, A007924, A050234, A066547.

A007923[n_Integer] := Module[{result = 0},Do[ result += (Mod[(n*(n - 1)/2 + i - 1), 9] + 1) * 10^(n - i),{i, 1, n}   ]; result ]; Table[A007923[n],{n,18}] (* James C. McMahon, Dec 04 2023 *)

a(n)=my(m=(n*(n+1)/2-1)%9); sum(k=0,n-1,10^k*((m-k)%9+1))

a(n) = (10^9+1) a(n-9) - 10^9 a(n-18), n>=18. - corrected by Michael Somos, Sep 28 2002
a(n) = Sum_{i=1..n} ((n*(n-1)/2+i-1 mod 9)+1)*10^(n-i). - Vedran Glisic, Apr 08 2011
a(n) = floor(10^(n*(n+1)/2)*123456789/999999999) - 10^n*floor(10^(n*(n-1)/2)*123456789/999999999). - Néstor Jofré, Jun 03 2017

A075058 Lexicographically earliest infinite sequence of distinct positive numbers with the property that every positive integer is a sum of distinct terms (see algorithm below).

Original entry on oeis.org

1, 2, 3, 7, 13, 23, 47, 97, 193, 383, 769, 1531, 3067, 6133, 12269, 24533, 49069, 98129, 196247, 392503, 785017, 1570007, 3140041, 6280067, 12560147, 25120289, 50240587, 100481167, 200962327, 401924639, 803849303, 1607698583, 3215397193, 6430794373

Offset: 0

Amarnath Murthy, Sep 07 2002

nonn

This sequence starts with a(0)=1, subsequent terms a(n) for n > 0 being obtained by selecting the greatest prime <= 1 + Sum_{i=0..n-1} a(i). This ensures that the sequence has the required property because Sum_{i=0..n-1} a(i) >= a(n) - 1, for all n >= 0 and a(0)=1, is a necessary and sufficient condition for it to hold.

			Given that the first 7 terms of the sequence are 1,2,...,23,47 then a(8)=(greatest prime) <= (1+2+...+23,47) + 1 = 97, hence a(8)=97.

Charles R Greathouse IV, Table of n, a(n) for n = 0..1000
Wikipedia, "Complete" sequence. [Wikipedia calls a sequence "complete" (sic) if every positive integer is a sum of distinct terms. This name is extremely misleading and should be avoided. - _N. J. A. Sloane_, May 20 2023]

Cf. A068524, A007924, A066352, A200947.

prevprime[n_Integer] := (j=n; While[!PrimeQ[j], j--]; j) aprime[0]=1; aprime[n_Integer] := (aprime[n] = prevprime[Sum[aprime[m], {m, 0, n - 1}] + 1]); Table[aprime[p], {p, 0, 50}]
a[0] = 1; a[n_] := a[n] = NextPrime[Sum[a[k], {k, 0, n-1}]+2, -1]; Table[a[n], {n, 0, 33}] (* Jean-François Alcover, Sep 30 2013 *)

print1(s=1);for(n=1,20,k=precprime(s+1);print1(", "k);s+=k) \\ Charles R Greathouse IV, Apr 05 2013

a(n) = (greatest prime) <= 1 + Sum_{i=0..n-1} a(i).

a(n) ~ k*2^n, with k roughly 0.748643. - Charles R Greathouse IV, Apr 05 2013

Entry revised by Frank M Jackson, Dec 03 2011

Edited by N. J. A. Sloane, May 20 2023

A185101 The number n written using the minimum number of terms in the base where the values of the places are 1 and primes (noncomposites). For multiple solutions the smallest binary value is chosen.

Original entry on oeis.org

0, 1, 10, 100, 101, 1000, 1001, 10000, 1100, 10010, 10100, 100000, 11000, 1000000, 100100, 1000010, 101000, 10000000, 110000, 100000000, 1010000, 100000010, 10001000, 1000000000, 1100000, 1000000010, 100010000, 1100100, 10100000, 10000000000

Offset: 0

Frank M Jackson, Jan 23 2012

nonn

There are many ways of generating binary vectors a(n) for selecting noncomposites that when summed give n. A007924 uses the greedy algorithm. The above sequence uses the strong Goldbach conjecture that any integer is the sum of at most three distinct summands. It generates a(n) to select the minimum number of distinct noncomposites. Where there are multiple solutions, it chooses the smallest binary vector.

			n=57 which is > 6 and odd, so m = (nextprime > 57/3) = 23 and n-m = 34 is even, thus A082467(17) = 6 and algorithm selects {23,11,23}. These are not distinct primes, so m = nextprime(nextprime > n/3) = 29 and A082467(14)=3, thus a(n) selects {29,11,17} as the binary vector 10010100000.

Eric Weisstein's World of Mathematics, Goldbach Conjecture.

Cf. A007924, A066352, A200947.

nextprime[j_] := Module[{k}, If[j==0, 1, (k=Floor[j]+1; While[!PrimeQ[k], k++]; k)]]; primetable[n_] := Module[{p, q}, Which[n==1, {0, 2, 0}, n==2, {1, 3, 0}, n==3, {1, 5, 0}, True, (p=n+1; q=2n-p; While[q>0&&!(PrimeQ[p]&&PrimeQ[q]), p++; q--]; {0, q, p})]]; fintable[m_] := Module[{temptable}, Which[m==0, {0, 0, 0}, m==1, {1, 0, 0}, PrimeQ[m], {0, m, 0}, PrimeQ[m-2]&&m>4, {0, 2, m-2}, EvenQ[m], primetable[m/2], True, (temptable=primetable[(m-nextprime[m/3])/2]; If[temptable[[3]]==nextprime[m/3], (temptable=primetable[(m-nextprime[nextprime[m/3]])/2]; temptable[[1]]=nextprime[nextprime[m/3]]), temptable[[1]]=nextprime[m/3]]; temptable)]]; decimal[t_] := Module[{temp2table, tempdecimal=0}, (temp2table=fintable[t]; If[temp2table[[1]]==0, Null, tempdecimal=tempdecimal+2^PrimePi[temp2table[[1]]]]; If[temp2table[[2]]==0, Null, tempdecimal=tempdecimal+2^PrimePi[temp2table[[2]]]]; If[temp2table[[3]]==0, Null, tempdecimal=tempdecimal+2^PrimePi[temp2table[[3]]]];tempdecimal)];Table[IntegerString[decimal[i], 2], {i, 0, 100}]

For n, 1 to 6, a(n) is manually defined. For n prime, a(n) selects n. For n > 6 and n-2 prime, a(n) selects 2 and n-2. For n > 6 and even, use A082467(n/2) to give k, then a(n) selects n/2+k, n/2-k. For n>6 and odd, let m = (nextprime > n/3), then n-m is even and A082467((n-m)/2) gives k, a(n) selects m, (n-m)/2-k, (n-m)/2+k. If m = (n-m)/2+k, then m = nextprime(nextprime > n/3) and repeat.

Name clarified by Frank M Jackson, Oct 08 2013

A201997 a(n) is the decimal value of the binary vector used to select terms of A075058 whose sum is n.

Original entry on oeis.org

0, 1, 2, 4, 5, 6, 7, 8, 9, 10, 12, 13, 14, 16, 17, 18, 20, 21, 22, 23, 24, 25, 26, 32, 33, 34, 36, 37, 38, 39, 40, 41, 42, 44, 45, 46, 48, 49, 50, 52, 53, 54, 55, 56, 57, 58, 60, 64, 65, 66, 68, 69, 70, 71, 72, 73, 74, 76, 77, 78, 80, 81, 82, 84, 85, 86, 87

Offset: 0

Frank M Jackson, Dec 07 2011

			For n=22, the binary vector when applied to A075058 is {0,1,0,1,1,0,...}, consequently 2+7+13=22. The decimal value of the binary vector (in ascending powers of 2) is 26, so a(22)=26.

Wikipedia, "Complete" sequence. [Wikipedia calls a sequence "complete" (sic) if every positive integer is a sum of distinct terms. This name is extremely misleading and should be avoided. - _N. J. A. Sloane_, May 20 2023]

Cf. A007924, A066352, A200947, A075058.

prevprime[n_Integer] := (j=n; If[n==1, 1, While[!PrimeQ[j], j--]; j]); aprime[n_Integer] := (aprime[n]=prevprime[Sum[aprime[m], {m, 0, n - 1}] + 1]); gentable[n_Integer] := (m=n; ptable={0}; While[m!=0, (i=0; While[aprime[i]<=m && ptable[[i + 1]]!=1, (AppendTo[ptable, 0];i++)]; ptable[[i]] = 1; m = m - aprime[i - 1])]; ptable); decimal[n_Integer] := (gentable[n]; Sum[2^(k-1)*ptable[[k]], {k, 1, Length[ptable]}]); aprime[0]=1; Table[decimal[r], {r,0,100}]

Binary(a(n)) x A075058 = n, where x is the inner product and the binary vector is in ascending powers of 2 with infinite trailing zeros.

Edited by N. J. A. Sloane, May 20 2023

A202618 a(n) is the smallest integer that is the sum of n distinct terms of A075058.

Original entry on oeis.org

0, 1, 4, 6, 19, 42, 89, 96, 289, 672, 1441, 2972, 6039, 12172, 24441, 48974, 98043, 196172, 392419, 784922, 1569939, 3139946, 6279987, 12560054, 25120201

Offset: 0

Frank M Jackson, Dec 21 2011

Any nonnegative integer can be written as a sum of distinct terms of A075058. a(n) is the smallest integer that is the sum of n distinct terms of A075058 in the same way that A066352 gives a Pillai sequence for the sequence comprising 1 followed by all the primes.

			For n=5, the binary vector at A201997(54) is the smallest binary vector containing 5 1's and when applied to A075058 selects the integer 42. Consequently because 42=23+13+3+2+1 and 1,2,3,13,23 are all terms of the complete sequence A075058, a(5)=42.

Wikipedia, "Complete" sequence. [Wikipedia calls a sequence "complete" (sic) if every positive integer is a sum of distinct terms. This name is extremely misleading and should be avoided. - _N. J. A. Sloane_, May 20 2023]

Cf. A007924, A066352, A200947, A075058, A201997.

prevprime[n_Integer] := (j=n;If[n==1, 1, While[!PrimeQ[j], j--]; j]);aprime[n_Integer] := (aprime[n]=prevprime[Sum[aprime[m], {m, 0, n - 1}]+1]);gentable[n_Integer] := (m=n;ptable={0};While[m!=0, (i=0;While[aprime[i]<=m && ptable[[i+1]]!=1, (AppendTo[ptable, 0];i++)];ptable[[i]] = 1;m=m-aprime[i - 1])];ptable);decimal[n_Integer] := (gentable[n];Sum[2^(k-1)*ptable[[k]], {k, 1, Length[ptable]}]);ones[n_Integer] :=(gentable[n];Sum[ptable[[k]], {k, 1, Length[ptable]}]);changeones[n_Integer] := (p = 0; While[ones[p] < n, p++]; p);aprime[0]=1;Table[changeones[r], {r, 0, 20}]

Find the smallest m such that binary(A201997(m)) x {1,1,1,...} = n, where x is the inner product, {1,1,1,1,...} is an infinite binary vector of 1's and binary(A201997(m)) a binary vector with infinite trailing zeros both in ascending powers of 2. Then a(n) = binary(m) x A075058, where x is the inner product and the binary vector is in ascending powers of 2 with infinite trailing zeros.

Edited by N. J. A. Sloane, May 20 2023

A205598 The number n written using a minimizing algorithm in the base where the values of the places are 1 and primes.

Original entry on oeis.org

0, 1, 10, 11, 101, 110, 111, 1010, 1011, 1101, 1110, 1111, 10110, 10111, 11010, 11011, 11101, 11110, 11111, 101011, 101101, 101110, 101111, 110110, 110111, 111010, 111011, 111101, 111110, 111111, 1011110, 1011111

Offset: 0

Frank M Jackson, Feb 08 2012

nonn

Any nonnegative number can be written as a sum of distinct primes + e, where e is 0 or 1 (see A007924, which uses a greedy algorithm for writing n). However in this sequence a(n) is generated by using a minimizing algorithm that gives the smallest binary vector for select members from the sequence Q = (1 union primes) that when summed gives n. Without the minimizing condition there is ambiguity -- for example, 8 = 7+1 = 5+3 = 5+2+1 has three representations.

			8 = 7+1 = 5+3 = 5+2+1, so a(8) = 1011.

Wikipedia, "Complete" sequence. [Wikipedia calls a sequence "complete" (sic) if every positive integer is a sum of distinct terms. This name is extremely misleading and should be avoided. - _N. J. A. Sloane_, May 20 2023]

Cf. A007924, A185101, A200947.

aprime[n_] := If[n==0, 1, Prime[n]]; seqtable[l_] := (stable=Table[aprime[j], {j, 0, l}]; stable); inttable[p_] := (itable=Reverse[IntegerDigits[p, 2]]; itable); h=1; otable={0}; ttable={}; While[h<100, (inttable[h]; seqtable[Length[itable]-1]; test=itable.stable; If[!MemberQ[ttable, test], AppendTo[otable, h], Null]; AppendTo[ttable, test]; h++)]; IntegerString[otable, 2]

Let Q be the ordered sequence of (1 union primes), then a(n) x Q = n, where x is the inner product and the binary vector a(n) is in ascending powers of 2 with infinite trailing zeros.

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A200947 Sequence A007924 expressed in decimal.

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A066352 Pillai sequence: a(n) is the smallest term in A007924 requiring n primes.

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A007923 Lengths increase by 1, digits cycle through positive digits.

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A075058 Lexicographically earliest infinite sequence of distinct positive numbers with the property that every positive integer is a sum of distinct terms (see algorithm below).

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A185101 The number n written using the minimum number of terms in the base where the values of the places are 1 and primes (noncomposites). For multiple solutions the smallest binary value is chosen.

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A201997 a(n) is the decimal value of the binary vector used to select terms of A075058 whose sum is n.

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A202618 a(n) is the smallest integer that is the sum of n distinct terms of A075058.

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