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A097021 Initial terms of chains consisting of five consecutive integers, for neither of which the value of sigma-function is divisible by six. 1

%I

%S 211248,1146096,3948048,6090048,14590800,54100800,61051248,315758448,

%T 567777600,1715222448,1912711248,2408874048,2636106048,2744664048,

%U 2811450096,3304032048,4647444048,4832821296,6020336448,6028239600,6739372800,7824754800,10110704400

%N Initial terms of chains consisting of five consecutive integers, for neither of which the value of sigma-function is divisible by six.

%C In A084301, that is among remainders of sigma(n) modulo 6, chains of 0's can be large. On the contrary, the length of non-0-remainder-chains is believed to be limited or occurrence of longer chains is rare. Consider remainders of sigma(5x) modulo 6.

%C The first 1000 terms are all divisible by 144. - _Donovan Johnson_, Aug 07 2013

%H Donovan Johnson, <a href="/A097021/b097021.txt">Table of n, a(n) for n = 1..1000</a>

%e n = 14590800: sigma values for {n, n+1, n+2, n+3, n+4} = {59658880, 15110144, 22806063, 20958080, 25533914} have remainders modulo 6 as follows {4,2,3,2,2}.

%o (PARI) forstep(m=25, 10110704400, 25, if(sigma(m)%6<>0, n=m; c=1; forstep(j=m-1, m-4, -1, if(sigma(j)%6<>0, c++; n=j, j=m-4)); for(j=m+1, m+4, if(sigma(j)%6<>0, c++, j=m+4)); if(c>=5, print1(n ", ")))) /* _Donovan Johnson_, Aug 06 2013 */

%Y Cf. A084301.

%K nonn

%O 1,1

%A _Labos Elemer_, Aug 23 2004

%E a(6)-a(20) from _Donovan Johnson_, Sep 03 2008

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Last modified December 3 00:23 EST 2022. Contains 358510 sequences. (Running on oeis4.)