login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A155561 Intersection of A000404 and A154777: N = a^2 + b^2 = c^2 + 2d^2 with a,b,c,d>0 2
17, 18, 34, 41, 68, 72, 73, 82, 89, 97, 113, 136, 137, 146, 153, 162, 164, 178, 193, 194, 225, 226, 233, 241, 242, 257, 272, 274, 281, 288, 289, 292, 306, 313, 328, 337, 353, 356, 369, 386, 388, 401, 409, 425, 433, 449, 450, 452, 457, 466, 482, 514, 521, 544 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..54.

EXAMPLE

a(1)=17 is the least number that can be written as A+B and C+2D where A,B,C,D are positive squares (namely 17 = 1^2 + 4^2 = 3^2 + 2*2^2).

a(2)=18 is the second smallest number which figures in A000404 and in A154777 as well.

PROG

(PARI) isA155561(n, /* use optional 2nd arg to get other analogous sequences */c=[2, 1]) = { for( i=1, #c, for( b=1, sqrtint((n-1)\c[i]), issquare(n-c[i]*b^2) & next(2)); return); 1}

for( n=1, 10^3, isA155561(n) & print1(n", "))

CROSSREFS

Sequence in context: A151978 A111054 A242975 * A231505 A022107 A041584

Adjacent sequences:  A155558 A155559 A155560 * A155562 A155563 A155564

KEYWORD

easy,nonn

AUTHOR

M. F. Hasler, Jan 24 2009

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified June 24 17:51 EDT 2021. Contains 345419 sequences. (Running on oeis4.)