■三角数=平方数(その44)
x^2-2y^2=+/-4
an+1+bn+1√2=(2+2√2)^n(an+bn√2)
=(2an+4bn)+(2an+2bn)√2
(2,2)
x^2-2y^2=4
an+1+bn+1√2=(6+4√2)^n(an+bn√2)
=(6an+8bn)+(4an+6bn)√2
(6,4)
p^2-2q^2=1のとき
(6p+8q)^2-2(4p+6q)^2=4p^2-8q^2=4
un+2=A^2un=(a+d)Aun-(ad-bc)Iun
=(a+d)un+1-(ad-bc)un
[6,8]
[4,6]=12un+1-4un
===================================
x^2-3y^2=4
an+1+√3bn+1=(4+2√3)(an+√3bn)
=(4an+6bn)+√3(2an+4bn)
(4,2)
p^2-3q^2=1のとき
(4p+6q)^2-3(2p+4q)^2=4p^2-12q^2=4
un+2=A^2un=(a+d)Aun-(ad-bc)Iun
=(a+d)un+1-(ad-bc)un
[4,6]
[2,4]=8un+1-4un
===================================
x^2-5y^2=+/-4
an+1+bn+1√5=(1+√5)(an+bn√5)
=(an+5bn)+√5(an+bn)
(1,1)
x^2-5y^2=4
an+1+bn+1√5=(3+√5)(an+bn√5)
=(3an+5bn)+√5(an+3bn)
(3,1)
p^2-5q^2=1のとき
(3p+5q)^2-5(p+3q)^2=4p^2-20q^2=4
un+2=A^2un=(a+d)Aun-(ad-bc)Iun
=(a+d)un+1-(ad-bc)un
[3,5]
[1,3]=6un+1-4un
===================================
x^2-6y^2=4
an+1+√6bn+1=(10+4√6)(an+√6bn)
=(10an+24bn)+√6(4an+10bn)
(10,4)
p^2-6q^2=1のとき
(10p+24q)^2-6(4p+10q)^2=4p^2-24q^2=4
un+2=A^2un=(a+d)Aun-(ad-bc)Iun
=(a+d)un+1-(ad-bc)un
[10,24]
[4,10]=20un+1-4un
===================================
x^2-7y^2=4
an+1+√7bn+1=(16+6√7)(an+√7bn)
=(16an+42bn)+√7(6an+16bn)
(16,6)
p^2-7q^2=1のとき
(16p+42q)^2-7(6p+16q)^2=4p^2-28q^2=4
un+2=A^2un=(a+d)Aun-(ad-bc)Iun
=(a+d)un+1-(ad-bc)un
[16,42]
[6,16]=32un+1-4un
===================================
x^2-8y^2=+/-4
an+1+√8bn+1=(2+√8)(an+√8bn)
=(2an+8bn)+√8(an+2bn)
(2,1)
x^2-8y^2=4
an+1+√8bn+1=(6+2√8)(an+√8bn)
=(6an+16bn)+√8(2an+6bn)
(6,2)
p^2-8q^2=1のとき
(6p+16q)^2-8(2p+6q)^2=4p^2-32q^2=4
un+2=A^2un=(a+d)Aun-(ad-bc)Iun
=(a+d)un+1-(ad-bc)un
[6,16]
[2,6]=12un+1-4un
===================================
x^2-10y^2=+/-4
an+1+bn+1√10=(6+2√10)(an+bn√10)
=(6an+20bn)+√10(2an+6bn)
(6,2)
x^2-10y^2=4
an+1+bn+1√10=(38+12√10)(an+bn√10)
=(38an+120bn)+√10(12an+38bn)
(38,12)
p^2-10q^2=1のとき
(38p+120q)^2-10(12p+38q)^2=4p^2-40^2=4
un+2=A^2un=(a+d)Aun-(ad-bc)Iun
=(a+d)un+1-(ad-bc)un
[38,120]
[12,38]=76un+1-4un
===================================