

A104149


Numbers n such that sigma(n+2) = sigma(n+1) + sigma(n).


3



1, 2, 22, 1966, 3262, 5014, 60454, 1016506, 4420162, 12055510, 14365606, 25726726, 27896422, 66562306, 72764734, 98734966, 175186654, 224868310, 253694926, 288657202, 386668342, 421575406, 504737746, 630645454, 1493547998, 1653797794, 2120325010, 2221315150
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OFFSET

1,2


LINKS

Donovan Johnson and Giovanni Resta, Table of n, a(n) for n = 1..95 (terms < 4*10^12, first 50 terms from Donovan Johnson)


FORMULA

a(n) = A065900(n)2 . [R. J. Mathar, Aug 19 2010]
a(n) = A076530(n)1 . [M. Hasler, Aug 19 2010]


EXAMPLE

sigma(22) = 1+2+11+22 = 36
sigma(23) = 1+23 = 24
sigma(24) = 1+2+3+4+6+8+12+24 = 60
sigma(24) = sigma(23) + sigma(22)


MAPLE

with(numtheory); A104149:=proc(i) local n;
for n from 1 to i do
if sigma(n+2)=sigma(n+1)+sigma(n) then print(n); fi;
od; end: A104149(10^9); # Paolo P. Lava, Apr 24 2013


PROG

(PARI) s1=1; s2=3; for(n=1, 10^8, s3=sigma(n+2); if(s3==s1+s2, print1(n ", ")); s1=s2; s2=s3) /* Donovan Johnson, Apr 08 2013 */


CROSSREFS

Sequence in context: A177410 A193486 A054948 * A113761 A054349 A182293
Adjacent sequences: A104146 A104147 A104148 * A104150 A104151 A104152


KEYWORD

nonn


AUTHOR

Neven Juric (neven.juric(AT)apisit.hr), Aug 16, 2010


EXTENSIONS

More terms from Zak Seidov and R. J. Mathar, Aug 19 2010


STATUS

approved



