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A261604 a(1)=0. For n>1, a(n) = smallest number > a(n-1) such that, for all m,r<n, a(n) != a(m)^2 + a(r)^2. 2
0, 1, 3, 4, 5, 6, 7, 8, 11, 12, 13, 14, 15, 19, 20, 21, 22, 23, 24, 27, 28, 29, 30, 31, 33, 35, 38, 39, 40, 42, 43, 44, 46, 47, 48, 51, 53, 54, 55, 56, 57, 59, 60, 62, 63, 66, 67, 68, 69, 70, 71, 75, 76, 77, 78, 79, 81, 82, 83, 84, 86, 87, 88 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

LINKS

Charles R Greathouse IV, Table of n, a(n) for n = 1..10000

Anders Hellström, Ruby program

FORMULA

a(n) ~ n, and in particular a(n) = n + O(n/sqrt(log n)). I do not know if this bound is tight. - Charles R Greathouse IV, Sep 01 2015

PROG

(PARI) issumsq(n, r, s)=(r^2)+(s^2)==n

first(m)=my(v=vector(m), x, r, n, s); v[1]=0; for(n=2, m, v[n]=v[n-1]+1; until(x==1, for(r=1, n-1, for(s=1, n-1, if(issumsq(v[n], v[r], v[s]), v[n]++; x=0; break(2), x=1))))); v;

(PARI) isA022544(n)=if(n%4==3, return(1)); my(f=factor(n)); for(i=1, #f~, if(f[i, 1]%4==3 && f[i, 2]%2, return(1))); 0

search(v, x)=my(t=setsearch(v, x)); if(t, t, setsearch(v, x, 1))

list(lim)=my(v=List([0, 1]), t); for(n=3, lim, if(isA022544(n), listput(v, n); next); for(j=search(v, sqrtint((n-1)\2)+1), search(v, sqrtint(n)), if(issquare(n-v[j]^2, &t) && setsearch(v, t), next(2))); listput(v, n)); Set(v) \\ Charles R Greathouse IV, Sep 01 2015

CROSSREFS

A022544 is a subsequence.

Cf. A026468, A026466, A026467, A026469, A026470.

Sequence in context: A001272 A273664 A047563 * A120561 A051016 A044951

Adjacent sequences:  A261601 A261602 A261603 * A261605 A261606 A261607

KEYWORD

nonn

AUTHOR

Anders Hellström, Aug 25 2015

STATUS

approved

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Last modified February 22 15:05 EST 2020. Contains 332137 sequences. (Running on oeis4.)