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.

A294174 Numbers that can be expressed both as the sum of first primes and as the sum of first composites.

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%I A294174 #34 Mar 11 2024 01:53:57
%S A294174 0,10,1988,14697,83292,1503397,18859052,93952013,89171409882,
%T A294174 9646383703961,209456854921713,3950430820867201,
%U A294174 13113506646374409451778
%N A294174 Numbers that can be expressed both as the sum of first primes and as the sum of first composites.
%e A294174 From _Jon E. Schoenfield_, Feb 10 2018: (Start)
%e A294174 10 is in the sequence because prime(1) + prime(2) + prime(3) = 2 + 3 + 5 = 10 and composite(1) + composite(2) = 4 + 6 = 10 (where composite(i) is the i-th composite number).
%e A294174 1988 is in the sequence because Sum_{i=1..33} prime(i) = A007504(33) = Sum_{i=1..51} composite(i) = A053767(51) = 1988.
%e A294174                           a(n) = A007504(j)
%e A294174    n         j         k       = A053767(k)
%e A294174   ==  ========  ========  =================
%e A294174    1         0         0                  0
%e A294174    2         3         2                 10
%e A294174    3        33        51               1988
%e A294174    4        80       147              14697
%e A294174    5       175       361              83292
%e A294174    6       660      1582            1503397
%e A294174    7      2143      5699           18859052
%e A294174    8      4556     12821           93952013
%e A294174    9    118785    403341        89171409882
%e A294174   10   1131142   4229425      9646383703961
%e A294174   11   5012372  19786181    209456854921713
%e A294174   12  20840220  86192660   3950430820867201 (End)
%t A294174 nextComposite[n_] := Block[{k = n + 1}, While[PrimeQ@k, k++]; k]; c = sc = 4; p = sp = 2; lst = {0}; While[p < 1000000000, If[ sc == sp, AppendTo[lst, sc]; c = nextComposite@c; sc += c]; While[ sp < sc, p = NextPrime@ p; sp += p]; While[ sc < sp, c = nextComposite@ c; sc += c]]; lst (* _Robert G. Wilson v_, Feb 11 2018 *)
%t A294174 Module[{pr=Accumulate[Prime[Range[5*10^7]]],co=Accumulate[Select[ Range[ 11*10^7], CompositeQ]]},Join[ {0},Intersection[pr,co]]] (* The program generates the first 12 terms of the sequence; to generate the 13th term increase the Range specifications substantially, but the program will take a long time to run. *) (* _Harvey P. Dale_, Sep 17 2019 *)
%Y A294174 Intersection of A007504 and A053767.
%Y A294174 Cf. A066527, A154587.
%K A294174 nonn,more,nice
%O A294174 1,2
%A A294174 _Max Alekseyev_, Feb 10 2018