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

211248, 1146096, 3948048, 6090048, 14590800, 54100800, 61051248, 315758448, 567777600, 1715222448, 1912711248, 2408874048, 2636106048, 2744664048, 2811450096, 3304032048, 4647444048, 4832821296, 6020336448, 6028239600, 6739372800, 7824754800, 10110704400

Offset: 1

Author

Labos Elemer, Aug 23 2004

Keywords

• nonn

Comments

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.

The first 1000 terms are all divisible by 144. - Donovan Johnson, Aug 07 2013

Examples

			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}.
		

Links

• Donovan Johnson, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A084301.

Programs

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 */

Extensions

a(6)-a(20) from Donovan Johnson, Sep 03 2008