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A004978 a(n)=least number m such that m-a(n-1) != a(j)-a(k) for all j,k less than n; a(1)=1, a(2)=2.
(Formerly N0416)
6
1, 2, 4, 8, 13, 21, 31, 45, 60, 76, 97, 119, 144, 170, 198, 231, 265, 300, 336, 374, 414, 456, 502, 550, 599, 649, 702, 759, 819, 881, 945, 1010, 1080, 1157, 1237, 1318, 1401, 1486, 1572, 1662, 1753, 1845, 1945, 2049, 2156, 2264 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

REFERENCES

N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).

LINKS

Nathaniel Johnston, Table of n, a(n) for n = 1..2000

G. E. Andrews, MacMahon's prime numbers of measurement, Amer. Math. Monthly, 82 (1975), 922-923.

PROG

(MATLAB) s=1:2000^2; d(1)=1; A004978(1)=1; A004978(2)=2;

for n=3:2000

  A004978(n)=A004978(n-1)+find([d, 0]~=s(1:max(size(d))+1), 1);

  d(end+1:end+n-1)=A004978(n)-A004978(1:n-1);

  d=sort(unique(d));

end

% Nathaniel Johnston, Feb 09 2011

CROSSREFS

Differences give A002048, see also A048201.

See also A001856.

For n>2, a(n) equals A002049(n-1)+1 and A048204(n-2)+2.

Sequence in context: A164508 A292774 A026039 * A005282 A046185 A259964

Adjacent sequences:  A004975 A004976 A004977 * A004979 A004980 A004981

KEYWORD

nonn

AUTHOR

N. J. A. Sloane. This was in the 1973 "Handbook", but was then dropped from the database. Resubmitted by Clark Kimberling. Entry revised by N. J. A. Sloane, Jun 10 2012

EXTENSIONS

Definition corrected by Bryan S. Robinson, Mar 16 2006

STATUS

approved

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Last modified June 19 17:22 EDT 2018. Contains 305594 sequences. (Running on oeis4.)