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A033913 Numbers n such that s(n)+s(n+1)+...+s(n+6)=t(n)+t(n+1)+...+t(n+6). 0
5, 11, 19, 133, 465, 1361, 1693, 205021, 317293, 2757669, 3104613, 12369341, 33468065, 187542277, 535082701, 821575373, 1310332017, 1454159241, 26789967589, 45217224437 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

a(21) > 10^11. - Donovan Johnson, Aug 15 2011

LINKS

Table of n, a(n) for n=1..20.

FORMULA

Here s(n)=sigma(n)-n, t(n)=|s(n)-n|.

MATHEMATICA

Select[Range[500000], Total[DivisorSigma[1, Range[#, #+6]]-Range[#, #+6]] == Total[ Abs[ DivisorSigma[ 1, Range[#, #+6]]-2Range[#, #+6]]]&]  (* Harvey P. Dale, Aug 14 2011 *)

PROG

(PARI) l=vector(7, n, abs(sigma(n)-2*n)-sigma(n)+n); l[7]=0; sc=sum(n=1, 7, l[n]); for(n=7, 1000000, m=sigma(n)-2*n; d=abs(m)-m-n; i=(n-1)%7+1; sc=sc-l[i]+d; l[i]=d; if(sc==0, print1(n-6, ", "))) (C. Ronaldo)

CROSSREFS

Sequence in context: A297365 A128927 A145934 * A088124 A029456 A304502

Adjacent sequences:  A033910 A033911 A033912 * A033914 A033915 A033916

KEYWORD

nonn

AUTHOR

Naohiro Nomoto

EXTENSIONS

More terms from C. Ronaldo (aga_new_ac(AT)hotmail.com), Jan 02 2005

a(10)-a(20) from Donovan Johnson, Aug 15 2011

STATUS

approved

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Last modified May 27 05:48 EDT 2020. Contains 334649 sequences. (Running on oeis4.)